Update Wiki about non-workspace users important instruction

Please add this important note to the wiki. (I couldn't figure out how to fork the Wiki)

`**Important note for GMail (@gmail.com / @googlemail.com) users**: If you don't use Google Workspace, Google forces your project to be "External" i.e. Public. Your project is placed into test mode by default, but **this will cause your tokens to expire after 7 days**, resulting in errors such as "**invalid_grant**". You **must publish your project** (via the OAuth consent screen settings) to prevent tokens from expiring after 7 days. Publishing the Google app does **not** allow public users to access your email.`

Thank you!

Update the project wiki with the provided note for Gmail and Google Workspace users. Review the OAuth consent screen guidance already present in the wiki, add the warning about test-mode token expiry and publishing, and verify that the note is visible and accurate.

Written by the indexing model from the issue text.