Feature Request: Source other configuration files

[Testare]

I have a set-up I use for most of my software where I keep common files with common configurations in one file, and then have them optionally source other configuration files for local-specific configurations. While there are other ways around it, I would like to do the same with my zellij configuration, but there doesn't seem to be a way to "source" other configuration files, much less optionally source them, and I think this might be a good feature to have =]