Amend documentation about CMD / ENTRYPOINT for CLI

[iquito]

When using the CLI images, it is implied that you should set a CMD (and this is shown in the one CLI example via command line), but it would help if at least one docker compose example and/or Dockerfile example showed this explicitely - it could be a CLI example running phpunit, which would be a common use case.

I tried setting up an ENTRYPOINT instead of a CMD, which overwrote the ENTRYPOINT of the image and lead to unexpected results (like php.ini settings not being set up), so a warning not to use ENTRYPOINT in a Dockerfile might also help, as most docker tutorials advise on using ENTRYPOINT instead of CMD, or using both together for executable containers.

[moufmouf]

Hey @iquito ,

Thanks for the advices. Indeed, a bit of work on the documentation is always good.
I opened this PR. #137

[iquito]

The PR solves this perfectly, thanks! And thanks for all the work on these great docker images in general, they are really useful.