Add Markdown linter to CI #14614

Type: other

I propose that the project incorporates a Markdown linter into the project's continuous integration system.

This would mean that PRs involving edits to Markdown files would be automatically checked for conformity with the project's Markdown style guide. This, in turn, would reduce the risk of a contributor, perhaps working in haste, failing to notice cases where their PRs do not (quite) meet the requirement's style guide (e.g. as in #14423, mea culpa) and thus using excessive reviewer time.