docs: add comments in pull request template

[wesleyboar]

Overview

Add comments to PR template, for new devs.

Note

💡 Ideas:

1. Should the comments be on one line <-- ... --> instead of three?

   • Easier to delete.
   • Less likely for markdown-noobs to change content in between <!-- and --> but still retain <!-- and -->.

2. Should headings match DesignSafe-CI's?

Related & Changes

• mimics docs: comment instructions for PR template DesignSafe-CI/portal#1710.
• keeps existing headings

Testing

0. Open rendering.
1. Comments are not visible.
2. Headings are unchanged.

UI

See rendering and raw markdown.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.08%. Comparing base (fef9bc2) to head (c5cfbbe).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1308   +/-   ##
=======================================
  Coverage   64.08%   64.08%           
=======================================
  Files         461      461           
  Lines       13785    13785           
  Branches     2748     2748           
=======================================
  Hits         8834     8834           
  Misses       4602     4602           
  Partials      349      349           

Flag	Coverage Δ
javascript	67.08% <ø> (ø)
unittests	60.91% <ø> (ø)

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