add buildProvider method on DockBlock for IDE support

[emrancu]

I have added buildProvider method on Socialite facade dockblock.

It will help IDE to suggest us the method exist.

We need buildProvider method for dynamic config ( redirect URL), specially for multitenant application.

[taylorotwell]

This doesn't exist on all providers?

[joelstein]

Thank you for this PR.

Can you post a code example of how to use buildProvider to customize the redirect URL?

[emrancu]

@joelstein Thank for approve my PR.

Here is example:

   $config =  config('services.google');
   $config['redirect'] = getCustomRedirectUrl();
   return Socialite::buildProvider(GoogleProvider::class, $config)->redirect();