Custom scopes for different requirements (iOS)

[AlvinTCH]

In the same manner as #267, I have moved the load function to a separate function and have configured the app to call the loadSignInClient function using data from

import { GoogleAuth } from '@codetrix-studio/capacitor-google-auth';

// use hook after platform dom ready
GoogleAuth.initialize({
  clientId: 'CLIENT_ID.apps.googleusercontent.com',
  scopes: ['profile', 'email'],
  grantOfflineAccess: true,
});

with fallback from the capacitor config

I will do the updating of the readme file when these two pull requests are merged in