Add handling of emqx and verdaccio for local testing

[knolleary]

A full FF install requires emqx and verdaccio to be running locally with particular configurations.

We have docs for setting up verdaccio (with the custom auth plugin), but not for emqx.

It would be best if the dev-env provided a simple one-command way of setting them both up.

### EMQX

• Assume docker is available (fail gracefully if not)
• copy the default config files in place
• provide start script to run
• include docs on how to customise the setup if other ports are needed etc

Verdaccio

ref FlowFuse/website#3010

• Add the auth plugin to the list of repos dev env includes
• Create working dir for verdaccio
• Build and install auth plugin
• provide start script to run
• include docs on how to customise the setup if other ports are needed etc

[knolleary]

Can be closed once #34 and #35 are merged