Update contribution guidelines for maintainers

Feature request

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Checklist

• This issue is not a duplicate, I've searched the Issue Tracker
• This issue is not a question, I'm aware that I can submit questions via Mastodon, Twitter, Email, Reddit or Matrix
• This issue is a content request, and not a bug report, feature request, or anything other

What are you missing or what could be improved?

Beyond existing guidelines for external contributors & translators, it would be nice to have the same kind of workflow for maintainers.

What is the solution you'd like to see?

1. Workflow describing how maintainers should contribute to the project (clone, pull, push to dev? or create issue branches & submit merge requests, like external contributors?)
2. Workflow describing how maintainers should handle Merge Requests
3. Workflow describing how to use Netlify's display previews for Merge Requests: https://docs.netlify.com/site-deploys/deploy-previews/
4. Workflow describing how to use Netlify's branch deploy for the dev branch: https://docs.netlify.com/site-deploys/overview/#branches-and-deploys
5. Workflow describing how maintainers should handle Releases (merge of dev & main branches)
6. Workflow describing how maintainers should handle Hotfixes to main
7. Instructions for maintainers concerning conflicts during merges

Do you have additional comments?

See Issue #8 (closed).