Customize PR instructions based on files modified

[anthonypz]

Fixes #5182 and #6778

What changes did you make?

• This change grabs a list of modified files submitted in the Pull Request (using the global github and context variables).
• Wrote logic to include the Pull Request and/or Contributor instructions based on the files modified in the PR.

Why did you make the changes (we will use this info to test)?

• These changes were made so that we can provide custom PR instructions to contributors and include relevant PR instructions based on which files were modified in the PR.

[github-actions[bot]]

Want to review this pull request? Take a look at this documentation for a step by step guide!

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From your project repository, check out a new branch and test the changes.

git checkout -b anthonypz-custom-pr-instructions-5182 gh-pages
git pull https://github.com/anthonypz/website.git custom-pr-instructions-5182

[t-will-gillis]

Hey @anthonypz Just did a live test for PR #6795, and the PR comment is posted as intended.

Thanks again for working on this and the fix- appreciate it! and thanks @tony1ee for your review