Add Dockerfile for local tests

[jkroepke]

Running rspec tests without setup a local environment.

Just run docker build . on the root from the module to see the test results.

[ekohl]

bundle exec release_checks covers all tests, including linting which you've now skipped I think.

[bastelfreak]

updated it

[ekohl]

We should add this to the .pmtignore so it's not shipped to the forge but otherwise I'd be OK with this.

[bastelfreak]

@ekohl updated it.

[ekohl]

Untested and not a big fan of so many small files, but not going to block it if it makes some peoples lives easier.

[bastelfreak]

I gave it a try and it worked. If any user has high experiences in docker he might come up with enhancements. Otherwise I think it's fine.

[dhoppe]

@ekohl The number of files is not important. It is much more about the number of layers which have been reduced by using bundle exec release_checks.

[ekohl]

@dhoppe I was talking about the number of files we modulesync. I want to keep that number as low as possible.

Recently you might have seen me remove a lot of them by making sure we can generate nodesets on the fly (with beaker-hostgenerator). This means we only need to update one gem rather than n modules. It also means the entire ecosystem can benefit.