Implement Tree.RemoveStyle

[raararaara]

What this PR does / why we need it?

• Added Tree.RemoveStyle & RHT.remove, which was implemented in go-sdk but not js-sdk.

Any background context you want to provide?

What are the relevant tickets?

Addresses #626
Related yorkie-team/yorkie#748

Checklist

• Added relevant tests or not required
• Didn't break anything

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (e636b3e) 81.22% compared to head (d479d55) 81.35%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/document/crdt/rht.ts	88.57%	1 Missing and 3 partials ⚠️
src/document/json/tree.ts	55.55%	2 Missing and 2 partials ⚠️
src/document/crdt/tree.ts	92.30%	0 Missing and 1 partial ⚠️
src/document/operation/tree_style_operation.ts	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #745      +/-   ##
==========================================
+ Coverage   81.22%   81.35%   +0.13%     
==========================================
  Files          59       59              
  Lines        4292     4344      +52     
  Branches      839      852      +13     
==========================================
+ Hits         3486     3534      +48     
  Misses        547      547              
- Partials      259      263       +4     

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[hackerwins]

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