[Bug] Base URL should be modified in the `/preview` command

[frank-zsy]

Are you certain it's a bug?

• [X] Yes, it looks like a bug

Are you sure this is not an issue in Docusaurus?

• [X] It is not a Docusaurus issue

Is there an existing issue for this?

• [X] I have searched existing issues, it hasn't been reported yet

Issue description

Without setting the correct base URL in the /preview command leads to broken redirections in the preview website, because all the redirection link will still point to the https://open-digger.cn/ which means we can not check the links in the preview website.

We should modify the base URL in the config file while deploying the preview website.