(msys2) Clarify where to raise issues

[pauby]

Description

I've updated the README.md file for msys2. These should flow into the 'description` in the .nupspec file.

Note that how we add this info, the message and the formatting are all up for debate. I wanted to get something up here for discussion. Once agreed, I feel we should require any updates to a package to add this to the README files (perhaps by adding it to #1754).

Motivation and Context

Questions are still being asked via Disqus for many packages. As Disqus is generally not responded to it makes sense to clarify where questions and issues should be raised. Going forward we should add this to all packages.

How Has this Been Tested?

I haven't tested this as it was an update to Markdown.

Screenshot (if appropriate, usually isn't needed):

N/A.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Migrated package (a package has been migrated from another repository)

Checklist:

• My code follows the code style of this repository.
• My change requires a change to documentation (this usually means the notes in the description of a package).
• I have updated the documentation accordingly (this usually means the notes in the description of a package).
• All files are up to date with the latest Contributing Guidelines
• The added/modified package passed install/uninstall in the chocolatey test environment.
• The changes only affect a single package (not including meta package).

[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[AdmiringWorm]

LGTM