Support Google Analytics 4 (GA 4)

According to [this document on Google Analytics Help](https://support.google.com/analytics/answer/11583528), the Universal Analytics (GA 3) will be going away on July 1, 2023:

- Until **July 1, 2023**, user can continue to use and collect new data in the Universal Analytics (GA 3) properties.
- After **July 1, 2023**, user will be able to access previously processed data in the Universal Analytics property for at least six months.

Google now strongly encourages users to export their historical reports during this time. And after that future date, users will no longer be able to see GA 3 reports in their dashboard (or accessing data via the API).

> HackMD/CodiMD only support GA 3 now and this feature should be updated or removed.