feat: add option to paste plain text

[asjqkkkk]

To fix #7023

Feature Preview

• add Paste as plain text item to ContextMenu
• pasting the original Markdown data will automatically convert it

PR Checklist

• My code adheres to AppFlowy's Conventions
• I've listed at least one issue that this PR fixes in the description above.
• I've added a test(s) to validate changes in this PR, or this PR only contains semantic changes.
• All existing tests are passing.

[github-actions]

🥷 Ninja i18n – 🛎️ Translations need to be updated

Project /project.inlang

lint rule	new reports	level	link
Missing translation	28	warning	contribute (via Fink 🐦)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.42%. Comparing base (171c563) to head (fabc1ca).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7045   +/-   ##
=======================================
  Coverage   64.41%   64.42%           
=======================================
  Files         280      280           
  Lines       10738    10738           
  Branches     1449     1449           
=======================================
+ Hits         6917     6918    +1     
  Misses       3648     3648           
+ Partials      173      172    -1     

Flag	Coverage Δ
appflowy_web_app	64.42% <ø> (+<0.01%)	⬆️

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