Add documentation for switching to Supabase

[dexsnake]

It would be great to see some documentation on swapping out Clerk and Neon to use Supabase for the auth and database.

[haydenbleasel]

I agree, had a few folks ask for this! I contacted the Supabase team on X about working together on it, no reply. Maybe I'll try here.

@kiwicopple @MildTomato @saltcod keen to collab?

[fmerian]

ping @awalias

[thedevdavid]

@haydenbleasel I have a very similar monorepo setup with Supabase, so I can help with this. A bit short on time now but I'm happy to do it over the next 2 weeks

[saltcod]

missed the ping @haydenbleasel (I'm quicker on twitter (@saltcod)!) what were you thinking?