Document exposing API and management ports when not using docker-compose.yaml

[pgporada]

#444 removed exposing the API and management ports directly in the Dockerfile in favor of the docker-compose.yml. Not everyone will be using docker compose so let's document how it should be done.

Fixes #452

[mcpherrinm]

It’s not quite so simple, because we use the same docker file for both pebble and pebble-challtestsrv

[pgporada]

We should split that apart then so they behave appropriately running as one-off docker run's or docker compose up.

[mcpherrinm]

EXPOSE is only really for the use docker run --publish-all instead of specifying the ports with -p, which is at most a minor inconvenience IMO, so we should consider how much extra complexity we want to add here to support that

[pgporada]

How about switching all the documented docker run steps to add in those ports?