Add API specification links to user guides

Add links to relevant API specification sections in documentation
guides to improve navigation between practical examples and detailed
API documentation.

This addresses issue 4347 by adding links to the following guides:
- HTTP feature guides (CORS, timeouts, method matching, etc.)
- gRPC and traffic splitting guides
- TLS configuration guide
- Getting started guide

All links follow the established pattern used in existing guides
and reference the correct v1 API types.

Fixes 4347

Signed-off-by:  YASHMAHAKAL <[email protected]>

Author: YASHMAHAKAL

site-src/guides/getting-started/simple-gateway.md

@@ -8,8 +8,8 @@ This guide is a great place to start if you are new to Gateway API. It shows the
 {% include 'standard/simple-gateway/gateway.yaml' %}
 ```
 
-The Gateway represents the instantiation of a logical load balancer and the
-GatewayClass defines the load balancer template when users create a Gateway.
+The [Gateway](../../reference/spec.md#gateway.networking.k8s.io/v1.Gateway) represents the instantiation of a logical load balancer and the
+[GatewayClass](../../reference/spec.md#gateway.networking.k8s.io/v1.GatewayClass) defines the load balancer template when users create a Gateway.
 The example Gateway is templated from a hypothetical `example`
 GatewayClass, which is meant to be a placeholder and substituted by users. Here
 is a list of available
@@ -21,10 +21,10 @@ The Gateway listens for HTTP traffic on port 80. This particular GatewayClass
 automatically assigns an IP address which will be shown in the `Gateway.status`
 after it has been deployed. 
 
-Route resources specify the Gateways they want to attach to using `ParentRefs`. As long as 
+Route resources specify the Gateways they want to attach to using [`ParentRefs`](../../reference/spec.md#gateway.networking.k8s.io/v1.ParentReference). As long as 
 the Gateway allows this attachment (by default Routes from the same namespace are trusted),
 this will allow the Route to receive traffic from the parent Gateway. 
-`BackendRefs` define the backends that traffic will be sent to. More complex 
+[`BackendRefs`](../../reference/spec.md#gateway.networking.k8s.io/v1.HTTPBackendRef) define the backends that traffic will be sent to. More complex 
 bi-directional matching and permissions are possible and explained in other guides.
 
 The following HTTPRoute defines how traffic from the Gateway listener is routed

site-src/guides/grpc-routing.md

@@ -1,7 +1,7 @@
 # gRPC routing
 
 The [GRPCRoute resource](../api-types/grpcroute.md) allows you to match on gRPC traffic and
-direct it to Kubernetes backends. This guide shows how the GRPCRoute matches
+direct it to Kubernetes backends. This guide shows how the [GRPCRoute](../reference/spec.md#gateway.networking.k8s.io/v1.GRPCRoute) matches
 traffic on host, header, and service, and method fields and forwards it to different
 Kubernetes Services.
 

site-src/guides/http-cors.md

@@ -8,7 +8,7 @@ Cross-Origin Resource Sharing (CORS). CORS is a security feature that allows
 or denies web applications running at one domain to make requests for resources
 from a different domain.
 
-The `CORS` filter in an `HTTPRouteRule` can be used to specify the CORS policy.
+The [`CORS` filter](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPCORSFilter) in an `HTTPRouteRule` can be used to specify the CORS policy.
 
 ## Allowing requests from a specific origin
 

site-src/guides/http-header-modifier.md

@@ -1,7 +1,7 @@
 # HTTP Header Modifiers
 
 [HTTPRoute resources](../api-types/httproute.md) can modify the headers of HTTP requests and the HTTP responses from clients.
-There are two types of [filters](../api-types/httproute.md#filters-optional) available to meet these requirements: `RequestHeaderModifier` and `ResponseHeaderModifier`.
+There are two types of [filters](../api-types/httproute.md#filters-optional) available to meet these requirements: [`RequestHeaderModifier`](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPHeaderFilter) and [`ResponseHeaderModifier`](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPHeaderFilter).
 
 This guide shows how to use these features.
 

site-src/guides/http-method-matching.md

@@ -4,7 +4,7 @@
     This feature is part of extended support. For more information on release channels, refer to our [versioning guide](../concepts/versioning.md).
 
 The [HTTPRoute resource](../api-types/httproute.md) can be used to match
-requests based on the HTTP method. This guide shows how to use this
+requests based on the [HTTP method](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPRouteMatch). This guide shows how to use this
 functionality.
 
 ## Matching requests based on the HTTP method

site-src/guides/http-query-param-matching.md

@@ -4,7 +4,7 @@
     This feature is part of extended support. For more information on release channels, refer to our [versioning guide](../concepts/versioning.md).
 
 The [HTTPRoute resource](../api-types/httproute.md) can be used to match
-requests based on query parameters. This guide shows how to use this
+requests based on [query parameters](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPQueryParamMatch). This guide shows how to use this
 functionality.
 
 ## Matching requests based on a single query parameter

site-src/guides/http-request-mirroring.md

@@ -3,8 +3,8 @@
 ???+ info "Extended Support Feature: HTTPRouteRequestMirror"
     This feature is part of extended support. For more information on release channels, refer to our [versioning guide](../concepts/versioning.md).
 
-The [HTTPRoute resource](../api-types/httproute.md) can be used to mirror
-requests to multiple backends. This is useful for testing new services with
+The [HTTPRoute resource](../api-types/httproute.md) can be used to [mirror
+requests](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPRequestMirrorFilter) to multiple backends. This is useful for testing new services with
 production traffic.
 
 Mirrored requests will only be sent to one single destination endpoint

site-src/guides/http-timeouts.md

@@ -4,7 +4,7 @@
     This feature is part of extended support. For more information on release channels, refer to our [versioning guide](../concepts/versioning.md).
 
 The [HTTPRoute resource](../api-types/httproute.md) can be used to configure
-timeouts for HTTP requests. This is useful for preventing long-running requests
+[timeouts](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPRouteTimeouts) for HTTP requests. This is useful for preventing long-running requests
 from consuming resources and for providing a better user experience.
 
 The `timeouts` field in an `HTTPRouteRule` can be used to specify a request

site-src/guides/tls.md

@@ -54,11 +54,11 @@ The use of `Terminate` on `TLSRoute` is available on `Extended` [Support Level].
 
 ## Downstream TLS
 
-Downstream TLS settings are configured using listeners at the Gateway level.
+Downstream TLS settings are configured using [listeners](../reference/spec.md#gateway.networking.k8s.io/v1.Listener) at the Gateway level.
 
 ### Listeners and TLS
 
-Listeners expose the TLS setting on a per domain or subdomain basis.
+Listeners expose the [TLS setting](../reference/spec.md#gateway.networking.k8s.io/v1.GatewayTLSConfig) on a per domain or subdomain basis.
 TLS settings of a listener are applied to all domains that satisfy the
 `hostname` criteria.
 
@@ -116,7 +116,7 @@ would be invalid.
 
 ## Upstream TLS
 
-Upstream TLS settings are configured using the `BackendTLSPolicy` attached to a
+Upstream TLS settings are configured using the [`BackendTLSPolicy`](../reference/spec.md#gateway.networking.k8s.io/v1.BackendTLSPolicy) attached to a
 `Service` via a target reference.
 
 This resource can be used to describe the SNI the Gateway should use to connect to the

site-src/guides/traffic-splitting.md

@@ -1,7 +1,7 @@
 # HTTP traffic splitting
 
 The [HTTPRoute resource](../api-types/httproute.md) allows you to specify
-weights to shift traffic between different backends. This is useful for
+[weights](../reference/spec.md#gateway.networking.k8s.io/v1.HTTPBackendRef) to shift traffic between different backends. This is useful for
 splitting traffic during rollouts, canarying changes, or for emergencies.
 The HTTPRoute`spec.rules.backendRefs` accepts a list of backends that a route
 rule will send traffic to. The relative weights of these backends define