Add release documentation

[ockham]

Based on my notes from a video call with @cbravobernal, and recent hands-on experience 😅

[github-actions]

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Props bernhard-reiter.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.61%. Comparing base (7b2e4fb) to head (5b4ce99).
⚠️ Report is 1 commits behind head on trunk.

Additional details and impacted files

@@             Coverage Diff              @@
##              trunk     #385      +/-   ##
============================================
- Coverage     53.58%   52.61%   -0.98%     
  Complexity     4419     4419              
============================================
  Files           298      298              
  Lines         39448    39448              
============================================
- Hits          21139    20754     -385     
- Misses        18309    18694     +385     

Flag	Coverage Δ
e2e-js	45.71% <ø> (-0.02%)	⬇️
e2e-php	40.45% <ø> (-1.58%)	⬇️
javascript	15.07% <ø> (ø)
phpunit	29.96% <ø> (ø)

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[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props bernhard-reiter.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.