Check that docker is running when running src batch

Created by: malomarrec

Current behaviour

If I run a src batch preview, but Docker is not running, I get a not very informative

❌ Error:
   exit status 2

This confuses users, and ... sure you need to RTFM, but that takes time. It's a very very frequent failure mode in first usage.

Proposed behaviour

Check that docker is running, and fail with an explicit error

Environemnt

MacBook Pro / M1