Update documentation to reflect that keycloak-nodejs-connect is no longer maintained

### Describe the bug

This component is no longer maintained, however the README.md in the project only states that it is deprecated:

> Warning This package is deprecated and will be removed in the future. We will shortly provide more details on removal date, and recommended alternatives.

Similarly, there's still a Keycloak guide for this component: https://www.keycloak.org/securing-apps/nodejs-adapter despite there not being a release since 26.1.1

### Version

SNAPSHOT

### Expected behavior

We should archive this repository and clearly state that the code is no longer maintained. The Keycloak guide should be removed or updated to convey this information. Pointers to existing NodeJS solutions for OIDC could also benefit users who need to migrate to a new solution.

### Actual behavior

_No response_

### How to Reproduce?

_No response_

### Anything else?

_No response_

Review README.md and the Keycloak NodeJS adapter guide linked in the issue to identify the current deprecation wording and guidance. Done means clearly stating that the component is no longer maintained, updating or removing the guide, and adding migration pointers to existing NodeJS OIDC solutions where appropriate.

Written by the indexing model from the issue text.