Static Asset Server to serve local versions of ontologies

[calummackervoy]

See discussion here: Multi-User-Domain/mud-jena#15 (comment)

@MattTennison

1. Use a environment variable for the vocab hosting endpoint here in mud-jena. For now, as we're using these GitHub branches, it could default to https://raw.githubusercontent.com/Multi-User-Domain/vocab/main
2. Run a static asset server (e.g. https://hub.docker.com/r/halverneus/static-file-server, or could write our own) to serve these .ttl files in development. Let's say we run it on port 7000 locally.
3. Change the environment variable for development to be http://localhost:7000, so responses reference ontologies from http://localhost:7000/mudchar.ttl instead of GitHub.

[MattTennison]

Point 2 could tie in nicely with Multi-User-Domain/mud-react#21 - we could create a docker-compose file that would let developers bring up all three repositories, and have them interact with each other by running a single command docker-compose up