Need 4.x tooltip html demo case #3898

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

In this document, it shows how to use html in tooltip. https://g2.antv.vision/zh/docs/manual/tutorial/tooltip#%E8%87%AA%E5%AE%9A%E4%B9%89-html-%E6%A8%A1%E6%9D%BF However, I copy the code and run in local, but it doesn't work. (Using @antv/g2@4.2.0)

The old site do provide some online case: https://antv.vision/old-site/g2/doc/tutorial/start/tooltip.html But the new site didn't.

What does the proposed API look like?

Need to update the document to provide an online demo case.

<!-- generated by antv-issue-helper. DO NOT REMOVE -->