Fix #960 by adding edited property to app_mention event payload

[seratch]

Summary

This pull request fixes #960 by adding edited property to AppMentionEvent interface. Refer to the issue for details.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

Merging #961 (c9108c1) into main (6b1ab43) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #961   +/-   ##
=======================================
  Coverage   66.19%   66.19%           
=======================================
  Files          13       13           
  Lines        1207     1207           
  Branches      356      356           
=======================================
  Hits          799      799           
  Misses        338      338           
  Partials       70       70           

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