Possibility to hide the email / password form on Login

Hi,
At Social Ministries we use Keycloak on internal apps where users can only connect through a custom identity provider (we don't have AgentConnect).
I customized the theme to add the following :
- new extra theme that doesn't display login form
- add a new env variable to add custom HTML below the login. We needed it to display a video to explain our users how to log in since our custom identity provider is a bit complicated.
- small CSS adjustment to add margin on social provider button
- add the displayName property from Keycloak realm as HTML title on the login page

I separated these changes into 4 commits. Do you think some or all of these changes could be added to the repo, or is it too custom ?
I'll make a PR, let me know if there's anything I can clean up.