Add Oauth2 providers

[elricco]

• add text field for images from other services

Add twitch via OAuth2 auth as login method

• adds value for yform Formbuilder
• adds settings file for oauth2_twitch
• add special Provider for twitch
• theoretically adding scopes - standard user:read:email is set via Provider
• add documentation

Add google via OAuth2 auth as login method

• adds value for yform Formbuilder
• adds settings file for oauth2_google
• add special Provider for google
• theoretically adding hostingDomain for Google Workspace users
• add documentation