feat: Support the edited and dismissed actions on PullRequestReviewEvent

[bananaappletw]

The pull_request_review webhook is delivered for three actions:

• submitted
• edited
• dismissed

PullRequestReviewEvent documented Action as always "submitted".

This adds Changes *EditChange. GitHub sends it on the edited action as
{"body": {"from": "..."}}, so users can now read the old review body.

References:

• GitHub webhook docs
  • pull_request_review
  • edited
  • dismissed
• Github OpenAPI schema edited.schema.json

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.57%. Comparing base (440bc88) to head (76a3fb2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4552   +/-   ##
=======================================
  Coverage   98.57%   98.57%           
=======================================
  Files         197      197           
  Lines       18252    18252           
=======================================
  Hits        17991    17991           
  Misses        261      261           

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[gmlewis]

Thank you, @bananaappletw!
LGTM.
Awaiting second LGTM+Approval from any other contributor to this repo before merging.

cc: @stevehipwell - @Not-Dhananjay-Mishra

[Not-Dhananjay-Mishra]

LGTM

[gmlewis]

Thank you, @Not-Dhananjay-Mishra!
Merging.