ignore/types: refactor lisp into scheme and lisp types

[jgarte]

This PR refactors and cleans up the lisp type and adds a new scheme type.

Scheme and Lisp (Common Lisp) should be kept separate conceptually as they are different languages. Additionally, Julia code should not show up when searching for Lisp code. We already have an elisp type, so people searching for Emacs Lisp code should use that type for clarity and intent.

Lisp type changes:

• Added *.asd (ASDF system definition files - the standard build system for Common Lisp)
• Removed *.el (use elisp type instead)
• Removed *.jl (Julia, not a Lisp in the strict sense and we already have a julia type)
• Removed *.sc and *.scm (moved to new scheme type)

New Scheme type added:

• *.scm - Standard Scheme source code
• *.sc - Scheme source (alternate, rare)
• *.sch - Scheme source (alternate, rare)
• *.sld - R7RS library definition files
• *.sls - R6RS library source files
• *.sps - R6RS program source files

References:

• ASDF: https://asdf.common-lisp.dev/
• Scheme file extensions registry: https://registry.scheme.org/ (See the Filename extensions section)
• R6RS specification: https://r6rs.org/
• R7RS specification: https://small.r7rs.org/