Documentation on multi-codebase environments?

I believe there should be docs on how to optimally setup workerd for multiple different JS codebases. Based on https://github.com/cloudflare/workerd/blob/main/src/workerd/server/workerd.capnp#L114-L115 it seems like we can't currently doing that using Host Headers natively, but can use a main javascript script to do so. Having an example of that would be ideal, otherwise my idea is to make a unix socket per site, and hook nginx into those.