* chore(lint): refactor Markdown linting to use markdownlint-cli2
- first commit is just config changes; lint updates will follow
* lint fixes
* fix markdownlint for rule MD045/no-alt-text
* lint config changes for prefering 'dash' style for rule MD004/ul-style
* lint:markdown:fix changes for MD004/ul-style
* manually apply this h3->h2 fix that Amir had in his #4703 PR
* mention markdown linting in the Linting section of the contributor guide
* add link to rules docs
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Co-authored-by: Marc Pichler <marc.pichler@dynatrace.com>
Svetlana Brennan