DRAFT: Add additional guidance for community MRs

What does this MR do and why?

Add additional guidance for community MRs. See the problem it solves #466728 (closed)

• Related to Add docs to the new Create merge request button... (#451432 - closed)
• Related to Docs: Add section to Merge Request Workflow to ... (#466728 - closed)

• Add engineering docs for assisting in community contributions

Changelog: changed

Existing Production docs: https://docs.gitlab.com/ee/development/code_review.html#taking-over-a-community-merge-request

MR acceptance checklist

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Before	After

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Related to #466728 (closed)