Add docker container to run Berp

[ehuelsmann]

🤔 What's changed?

A dockerized version of Berp.

⚡️ What's your motivation?

The cucumber/build container is huge. Most people only need it to run Berp. So, instead of downloading and maintaining a multi-gigabyte container, lets use a lean one with exactly one purpose.

🏷️ What kind of change is this?

• :bank: Refactoring/debt/DX (improvement to code design, tooling, documentation etc. without changing behaviour)

♻️ Anything particular you want feedback on?

This container likely causes permissions conflicts: the cukebot user has hard-coded UID 1000 whereas not everybody will be running as that user. The release container had trickery to be able to run "as the current user". Is it easy to transplant and do we want/need that? (was it even in the container? Or was it in the makefile before?)

📋 Checklist:

• [x] I agree to respect and uphold the Cucumber Community Code of Conduct

[ehuelsmann]

Branch rebased (explaining the force-push).

[mpkorstanje]

Cheers @ehuelsmann ! Took me a while to get to this but this is actually really good improvement. A belated thanks for kicking it off.