Salt: Contributing Docs do not mention changelog

[sagetherage]

Description of Issue

Changelog is in use and to add to the log it is more than a commit message, we should have that documented in the docs

Setup

https://docs.saltstack.com/en/latest/topics/development/contributing.html#sending-a-github-pull-request

Steps to Reproduce Issue

N/A

Versions Report

N/A

[sagetherage]

@saltstack/docs-working-group

[sagetherage]

do we also need information on towncrier in the contributing docs?

[ScriptAutomate]

The good thing is that the following can be used:

:ref:`changelog`

As towncrier changelog directions were added via #56984, this should now be an easier fix since we'd be able to insert it as a simple reference. In order to avoid merge conflicts, this is currently blocked by #57645