[Documentation Update]: Update contribution Q&A for stale PRs

[eriqua]

Check for previous/existing GitHub issues

• [x] I have checked for previous/existing GitHub issues

Description

Update contribution Q&A wiki page with guidelines on how to take over stale PRs from unresponsive authors

If

• the contribution is useful but would require updates
• PR authors are unresponsive to suggested comments

Then module owners are allowed to take over the PR

• merge author's branch to a newly created branch
• work on the codebase from there
• open a new PR. If the original PR was attached to an issue intending to close it, do the same with the new PR
• close the original PR with a comment referencing the new PR

[microsoft-github-policy-service[bot]]

[!IMPORTANT] The "Needs: Triage :mag:" label must be removed once the triage process is complete!

[!TIP] For additional guidance on how to triage this issue/PR, see the AVM Issue Triage documentation.