Specify "MP_JWT_VERIFY_PUBLICKEY" as a requirement or remove the dependency

[FullLifeGames]

When you currently try to pull and run the docker image of trellisldp/trellis-triplestore (or try to build and run trellis on your own), it will always throw an error that it cannot find the public key location (since it is per default set to changeme) (at least on Windows).

For fixing this, one needs to set the "MP_JWT_VERIFY_PUBLICKEY" (mp.jwt.verify.publickey) environment variable to make it run, which is not documented anywhere.

The workflow to run trellis looks like this:

docker pull trellisldp/trellis-triplestore:develop
docker run -p 8080:8080 -e MP_JWT_VERIFY_PUBLICKEY="{publicKey}" -d trellisldp/trellis-triplestore:develop

Since I had some trouble figuring this out, it would be good to document this on the Dockerhub page or remove the dependency on setting this key (e.g. use a valid default key) because I cannot image I would be the only one which has this issue.