Find a way to custom the keycloak UI

[dadiorchen]

There are some articles that discuss this: https://alxrodav.medium.com/keycloak-custom-login-theme-21be10ad3f4

We need to go through this so we can find a workflow to do the customization.

Basically, we just need to define a workflow or set up the environment so the HTML developer can join in to do the UI work.

[dadiorchen]

This can be done by #191 basically, we need to add an extra step when deploying the keycloak, to run a shell script/commands to add some file under a folder of the container, maybe in the future we can find a better way like generate new image for this, but for a quick solution, we can do this way, (run commands)