ci: make signed commits when publishing docs

[dsanders11]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.

Summarize your changes:

malept/github-action-gh-pages stages the changes to commit, and dsanders11/github-app-commit-action commits them.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.80%. Comparing base (d143d65) to head (d93aa38).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1682   +/-   ##
=======================================
  Coverage   91.80%   91.80%           
=======================================
  Files          16       16           
  Lines         854      854           
  Branches      167      167           
=======================================
  Hits          784      784           
  Misses         52       52           
  Partials       18       18           

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[continuous-auth]

🎉 This PR is included in version 18.2.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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