Docs: point users to the latest and greatest cpp-rs-driver

[tzach]

There should be a visible link from README and About to the new
https://cpp-rs-driver.docs.scylladb.com/stable/

Doc site should include a note (example) below pointing users to the new driver

[roydahan]

@wprzytula can you please take care of it?

[wprzytula]

Doc site should include a note (example) below pointing users to the new driver

@dgarcia360 , can you assist in adding such a note to the CPP Driver docs?

[tzach]

@dgarcia360 this is similar to scylladb/scylladb#22636 redirection between old and new doc sites