Resolve "Combine all GitLab workflow documentation to CONTRIBUTING.md"

What does this MR do?

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #30141 (closed)

added 3 commits

• 7a47d198 - Move retro/kickoff doc to PROCESS.md
• 15369816 - Improve the merge request guidelines and DoD in CONTRIBUTING.md
• 8f694c9d - Improve the Code review guidelines documentation

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added 3 commits

• 667a20dc - Move retro/kickoff doc to PROCESS.md
• bcf63ff7 - Improve the merge request guidelines and DoD in CONTRIBUTING.md
• 111b8651 - Improve the Code review guidelines documentation

Compare with previous version

added 4 commits

• ccb8e693 - Document labels in CONTRIBUTING.md
• 5cbb11a7 - Move retro/kickoff doc to PROCESS.md
• 52310ac0 - Improve the merge request guidelines and DoD in CONTRIBUTING.md
• 16d7a899 - Improve the Code review guidelines documentation

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added 1 commit

• b26d7523 - Update ToC of CONTRIBUTING.md and PROCESS.md

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mentioned in merge request gitlab-com/www-gitlab-com!5815 (merged)

added 4 commits

• 11661d1d - Move retro/kickoff doc to PROCESS.md
• 0374e22a - Improve the merge request guidelines and DoD in CONTRIBUTING.md
• f644b8c8 - Improve the Code review guidelines documentation
• cb87903c - Update ToC of CONTRIBUTING.md and PROCESS.md

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@rspeicher Could you please review this one and https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/5815 (they're should go in together)? Thanks!

assigned to @rspeicher

unmarked as a Work In Progress

@rymai LGTM, just a few suggestions. 👍

assigned to @rymai

@rspeicher Thanks, feedback addressed! :)

assigned to @rspeicher

added 1 commit

• 38c29f87 - Improving copy of CONTRIBUTING.md, PROCESS.md, and code_review.md

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I believe the conflict in CONTRIBUTING.md from ee_compat_check can be ignored since the file should be the same in EE anyway.

resolved all discussions

approved this merge request

merged

mentioned in commit 985737fd