feat: support view diffs between post content versions

[guqing]

What type of PR is this?

/kind feature
/area core
/milestone 2.16.x

What this PR does / why we need it:

支持查看文章内容版本间的差异比较功能

Which issue(s) this PR fixes:

Fixes #5849

Does this PR introduce a user-facing change?

支持查看文章内容版本间的差异比较功能

[f2c-ci-robot]

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[codecov]

Codecov Report

Attention: Patch coverage is 53.48837% with 40 lines in your changes are missing coverage. Please review.

Project coverage is 56.51%. Comparing base (5fdf6c0) to head (a1ff7d7).
Report is 162 commits behind head on main.

Files	Patch %	Lines
...a/run/halo/app/content/AbstractContentService.java	22.22%	20 Missing and 1 partial ⚠️
...ava/run/halo/app/content/impl/PostServiceImpl.java	0.00%	10 Missing ⚠️
...halo/app/core/extension/endpoint/PostEndpoint.java	71.42%	8 Missing ⚠️
...src/main/java/run/halo/app/content/PatchUtils.java	95.23%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5892      +/-   ##
============================================
- Coverage     56.91%   56.51%   -0.41%     
- Complexity     3319     3473     +154     
============================================
  Files           587      612      +25     
  Lines         18968    20559    +1591     
  Branches       1401     1422      +21     
============================================
+ Hits          10795    11618     +823     
- Misses         7594     8359     +765     
- Partials        579      582       +3     

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.2% Duplication on New Code

See analysis details on SonarCloud

[guqing]

尝试了一下，无法在后端实现此功能，可能在前端实现更合适，将 html 内容转为 Dom 树比较节点之后添加 class 属性，因此我将关闭此 PR