Move Keycloak JS into a seperate repository

[mposolda]

This task is about moving keycloak.js adapter into the repository https://github.com/keycloak/keycloak-js . It will probably consist of 2 sub-tasks:

• Move the adapter to the new repository
• Remove the adapter from the keycloak/keycloak repository

It seems that 2nd sub-task can be done once we are able to release keycloak.js from it's own repository (So after #2 ). We probably cannot remove keycloak.js from the main repository earlier, so we are able to release keycloak.js at any time (in case of some critical CVE or whatever)

It seems the order of tasks might be like:

• Introduce keycloak.js into new repository: Add keycloak.js adapter to the new repository #1
• Then make sure that it is possible to release: Create workflows to release Keycloak JS from own repo #2
• Then remove from keycloak/keycloak: Remove keycloak.js adapter from keycloak/keycloak repository keycloak#36645