OAuth PKCE flows when using `createClient`

# Improve documentation ## Link High level would be good: https://github.com/supabase/supabase/blob/master/apps/docs/content/guides/auth/social-login.mdx Definitely would be helpful in the server examples on the individual providers, or have a common example with all the required setup code that these could link to. https://github.com/supabase/supabase/blob/master/apps/docs/content/guides/auth/social-login/auth-google.mdx ## Describe the problem [discord thread here](https://discord.com/channels/839993398554656828/1413577005513052251) There are many threads across the internet with the same issue, where Supabase is redirecting a Google PKCE flow to their configured redirect url, but all values are sent like `<redirect_url>#access_token=<value>&<etc.>` instead of `<redirect_url>?code=<OTP>`. Some have options that worked for them, but didn't work for a lot of other people. To amplify the problem, we already had PKCE working for us with Supabase auth, so it was a conundrum. ## Describe the improvement The call to `createClient` needs to configure auth to use the `pkce` flow. Example: ```ts import { createClient } from '@supabase/supabase-js'; createClient( <supabaseUrl>, <supabaseAnonKey>, { auth: { flowType: 'pkce' } }) ``` ## Additional context This was not needed in the non-OAuth PKCE flows. I did find this in the [supabase client documentation](https://supabase.com/docs/reference/javascript/auth-exchangecodeforsession), but there was no mention of it in the OAuth overview examples for server.