chore(supabase_flutter): Updates README.md to include instructions on how to add native Google login (#521)

* feat: add

* updated readme to add google login related section

* updated the readme for auth section

* chore: clean up database methods

* simplify sample code

* minor example fix

* add note about deep link config

* add more details on deep link config

* bring deep link config up and remove auth deep dive

* Add instruction to set app auth redirect scheme

* remove signInWithGoogle()

* updated readme.md instructions on how to perform Google login

* remove appauth and package info plus

* revert example changes

* revert removing the experimental flag from signInWithApple

* revert other minor changes

* revert changes to add accessToken parameter to gotrue signInWithIdToken

* add link to appauth

* minor refactor around client ID

* get rid of platform specific setup instructions for app_auth

* Update packages/supabase_flutter/README.md

Co-authored-by: Vinzent <[email protected]>

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Co-authored-by: Vinzent <[email protected]>

Author: dshukertjr