feat: enable markdown linter for kits

[mhellmeier]

Description

This PR enables the markdown linter for the KITs.

Fixes #673

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files

[SebastianBezold]

👍 I think it is the best option to merge it, even with failing check. These issues did pile up due to the lack of linting and should now be worked on collectively.

Separate issues per KIT would be fine in my opinion.

[maximilianong]

Looks like all open PRs are now failing due to this new rule. How to handle this? Should we inform now the responsible of every KIT to resolve their issues?

[arnoweiss]

I don't have fundamental problems with merging despite a failed linter check. But there should be a requirement that every update to every kit fixes THEIR issues for ALL releases.

[mhellmeier]

Looks like all open PRs are now failing due to this new rule. How to handle this? Should we inform now the responsible of every KIT to resolve their issues?

Exactly, @maximilianong! Every KIT has to fix its linting errors. @SebastianBezold and I are planning to create a GitHub Issue for every KIT. It is important that this will be checked during the Quality Gates.

I don't have fundamental problems with merging despite a failed linter check. But there should be a requirement that every update to every kit fixes THEIR issues for ALL releases.

The first part is correct, @arnoweiss: While the KIT developers are fixing their linting problems, merging with a failed pipeline is okay. For the second part: Since the current pipeline only checks the docs and the docs-kits folder and not the docs-kits_versioned_docs, only the current and future KIT versions need to be corrected. Fixing the old archived versions would be great, but is still optional.