We're missing some configs from `docker-development` environment, which
causes a launch to fail.

Mount the application:  This loads the application into the running
docker image, allowing the running image to do the expected rails
development environment thing of seeing your code changes.

Run as the current user:  this (attempts) to prevent files owned by root
from being left on the filesystem.

cache mounts:  these will keep installed gems and node modules
avavilable, so we don't have to grab and reinstall on every rebuild.