Add a barebone lint step

[Jorg88]

Just a small draft pr to showcase how a new stage (in this case linting) would look.

[github-actions]

Package	Line Rate	Health
src.mpyl	92%	➖
src.mpyl.artifacts	60%	❌
src.mpyl.cli	61%	❌
src.mpyl.projects	95%	➖
src.mpyl.reporting	100%	✔
src.mpyl.reporting.formatting	99%	✔
src.mpyl.stages	63%	❌
src.mpyl.steps	88%	➖
src.mpyl.steps.build	82%	➖
src.mpyl.steps.deploy	73%	❌
src.mpyl.steps.deploy.bpm	62%	❌
src.mpyl.steps.deploy.k8s	81%	➖
src.mpyl.steps.deploy.k8s.resources	97%	➖
src.mpyl.steps.lint	90%	➖
src.mpyl.steps.postdeploy	82%	➖
src.mpyl.steps.test	93%	➖
src.mpyl.utilities	100%	✔
src.mpyl.utilities.bpm	77%	❌
src.mpyl.utilities.dagster	71%	❌
src.mpyl.utilities.github	74%	❌
src.mpyl.utilities.helm	100%	✔
src.mpyl.utilities.http_client	95%	➖
src.mpyl.utilities.jenkins	69%	❌
src.mpyl.utilities.junit	97%	➖
src.mpyl.utilities.logging	78%	❌
src.mpyl.utilities.pyaml_env	100%	✔
src.mpyl.utilities.repo	65%	❌
src.mpyl.utilities.sbt	96%	➖
src.mpyl.utilities.subprocess	76%	❌
src.mpyl.utilities.yaml	100%	✔
Summary	81% (3018 / 3725)	➖

Minimum allowed line rate is 79%

[github-actions]

New release 448.4132 deployed at Test Pypi.
Install with

pip install -i https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple mpyl==448.4132

[ptab]

Required for:

• https://github.com/Vandebron/Vandebron/pull/15597