Update documentation on creating release.

[josephsnyder]

Add information about the steps with CastXMLSuperbuild and the upload to
data.kitware.com

Add a warning about the "empty-ing" of the Win32 variable when executing
the script in this repository.

[jcfr]

Thanks for working on this 🙏

Before we move forward with integration, here are few nitpicks to address

[jcfr]

Instead, let's fix the script:

CastXML-python-distributions/scripts/update_castxml_version.py

Lines 93 to 94 in 37c6977

	set(win32_binary_url "NA") # Windows 32-bit binaries not available
	set(win32_binary_sha512 "NA")

In the commit message updating the script, reference issue #5

Suggested change:

-      set(win32_binary_url    "NA")  # Windows 32-bit binaries not available
+      set(win32_binary_url    "${win64_binary_url}")  # See https://github.com/CastXML/CastXML-python-distributions/issues/5
-      set(win32_binary_sha512 "NA")
+      set(win32_binary_sha512 "${win64_binary_sha512}")

For some more context, see e03b460#diff-aa166f56653254a5ea3d6db905d61992

[jcfr]

Let's move this directly into https://github.com/CastXML/CastXMLSuperbuild/blob/master/README.rst adding a section like

Maintainers
-----------

* `How to update CastXML version ? <https://github.com/CastXML/CastXMLSuperbuild/blob/master/docs/make_a_release.rst>`_
* `How to make a release ? <https://github.com/CastXML/CastXMLSuperbuild/blob/master/docs/update_castxml_version.rst>`_

[jcfr]

create the folder ``vX.Y.Z``

[johnwparent]

Release creation procedure is diverging significantly, closing as out of date.