Add HeiBai Theme

[NeoWangs]

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

[EasonWangs]

Heads-up for maintainers: the tester failure here is not specific to this PR.

The Tester workflow runs on pull_request_target and uses actions/checkout@v7 to check out the PR merge ref. Recent versions of actions/checkout refuse to check out fork PR code in a pull_request_target context unless allow-unsafe-pr-checkout: true is explicitly set (see https://gh.io/securely-using-pull_request_target), so the step fails immediately:

Error: Refusing to check out fork pull request code from a 'pull_request_target' workflow.

This affects every PR from a fork — e.g. #2576 fails the same way. Fixing it would mean either opting in with allow-unsafe-pr-checkout: true (with appropriate hardening) or switching the workflow back to the pull_request trigger.

FWIW the Netlify deploy preview for this PR builds fine: https://deploy-preview-2578--hexo-site.netlify.app

[github-actions]

✅ Theme thumbnails validation completed.

[stevenjoezhang]

@NeoWangs HeiBai.yaml is in wrong directory