feat(helper/toc): more flexible class name (hexojs/hexo#5010)

[renbaoshuo]

ref: hexojs/hexo#5010

Check List

Please read and check followings before submitting a PR.

• I want to publish my theme on Hexo official website.
  • I have read the theme publishing doc.
  • name is unique.
  • link URL is correct.
  • preview URL is correct.
  • preview URL web site is rendered correctly.
  • Add a screenshot to source/themes/screenshots.
  • Screenshot filename is same as value of name.
  • Screenshot size is 800 * 500.
  • Screenshot file format is png.
• I want to publish my plugin on Hexo official website.
  • I have read the plugin publishing doc.
  • name is unique.
  • link URL is correct.
• Others (Update, fix, translation, etc...)
  • Languages:
  • en English
  • ko Korean
  • pt-br Brazilian Portuguese
  • ru Russian
  • th Thai
  • zh-cn simplified Chinese
  • zh-tw traditional Chinese

[github-actions]

Theme name validation passed.
Theme thumbnails validation completed.

[renbaoshuo]

This pull request could be merged after hexojs/hexo#5043.