chore: use GitHub actions to sanitize themes & plugins list

[stevenjoezhang]

I have improved a script I wrote earlier that can automatically check whether the links for themes and plugins have been updated or become invalid, and it periodically opens a pull request to update them.

See https://github.com/hexojs/site/pull/1458#issuecomment-650570884

[github-actions[bot]]

Theme thumbnails validation completed.

[stevenjoezhang]

We previously discussed the issue of theme preview websites becoming unavailable (in https://github.com/hexojs/site/pull/1941#issuecomment-1321896950), and currently, dozens of theme preview websites are either down or redirected, with some even being maliciously registered due to expired domains. The main problem now is that it requires a significant amount of manual effort to determine whether these invalid links are due to slow access speeds leading to timeouts, or if they are no longer in use. I was thinking that perhaps we could use the now-discontinued hexojs.github.io domain to deploy preview sites for third-party themes. (See https://github.com/orgs/hexojs/discussions/5409)

[stevenjoezhang]

Another issue is that there are more than 60 repositories of themes or plugins are archived. I suggest that for repositories that are archived or have not been updated for a certain period (for example, 3 years), we need to provide a notice on the hexo.io website that the theme may no longer be available, or just remove them.

[uiolee]

use the now-discontinued hexojs.github.io domain to deploy preview sites for third-party themes.

If really necessary, it is better to use the repository page hexojs.github.io/<repo>/. At the same time, code security need to be considered.

theme preview websites becoming unavailable

To avoid this, I recommend that request the authors to use github action to build previews site in their own github page. We can add guide to https://hexo.io/docs/themes#Publishing