[Docs] Missing Environment Variables in "Configure and run your server"

[Geeknasty]

The documentation for Dedicated Servers currently lacks several environment variables supported by the KYBER Docker image. I have prepared a PR to update the "Environment variables" table to include the following missing entries:

• KYBER_SERVER_PASSWORD: Documentation for setting a server password.

• KYBER_SERVER_PLUGINS_PATH: Documentation for mounting server plugins.

• KYBER_MODULE_CHANNEL: Instructions for specifying release channels (e.g., stable, beta).

• KYBER_LOG_LEVEL: Logging verbosity options.