Warn that default signOut scope revokes all sessions. Motivation:
https://github.com/supabase/ssr/issues/68
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Documentation**
* Clarified that signing out without a specified scope ends all sessions
by default.
* Added guidance for using a local sign-out scope to preserve sessions
on other devices and browsers.
* Documented the invalid refresh token errors that may occur when other
sessions are revoked.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Katerina Skroumpelou