[2.x] Add documentation sync workflow

[emmadesilva]

Introduced a GitHub Actions workflow to automatically sync documentation from the monorepo to the hydephp/docs repository for relevant branches.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (9c26436) to head (6522038).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##              master     #2306   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity      2001      2001           
===========================================
  Files            197       197           
  Lines           5180      5180           
===========================================
  Hits            5180      5180           

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