feat: add the clear format function to the default rich text editor

[LIlGG]

What type of PR is this?

/kind feature
/area editor
/milestone 2.15.x

What this PR does / why we need it:

为默认富文本编辑器添加清除格式的功能。快捷键为 Mod + \。

How to test it?

输入文本，使用加粗、链接、斜体等 mark 相关功能，之后使用清除格式，查看格式是否被清除。

Which issue(s) this PR fixes:

Fixes #5684

Does this PR introduce a user-facing change?

为默认富文本编辑器添加清除格式的功能。

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.57%. Comparing base (5fdf6c0) to head (339f9dd).
Report is 103 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5685      +/-   ##
============================================
- Coverage     56.91%   56.57%   -0.35%     
- Complexity     3319     3325       +6     
============================================
  Files           587      595       +8     
  Lines         18968    19250     +282     
  Branches       1401     1357      -44     
============================================
+ Hits          10795    10890      +95     
- Misses         7594     7797     +203     
+ Partials        579      563      -16     

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[guqing]

/lgtm

[ruibaby]

/lgtm

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.3% Duplication on New Code

See analysis details on SonarCloud

[ruibaby]

/lgtm

[ruibaby]

/approve

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ruibaby

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• ui/OWNERS [ruibaby]

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