Add markdownlint to pre-commit

[IshaanDesai]

Checklist:

• I made sure that the CI passed before I ask for a review.
• I added a summary of the changes (compared to the last release) in the CHANGELOG.md. not a user-side change.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.

[Snapex2409]

Only one question:
Does this then make the Github Action "Lint Markdown Files" obsolete?

[IshaanDesai]

Only one question: Does this then make the Github Action "Lint Markdown Files" obsolete?

No, because not everyone has pre-commit installed, so I would still keep the Action as a safeguard. Yes indeed, because we run pre-commit via Actions. I will remove the Action workflow via this PR only.