Document how to require approval before a workflow runs

[jsoref]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/actions/how-tos/write-workflows/choose-when-workflows-run

What part(s) of the article would you like to see updated?

Add a page "Require manual approval for a specific job"

Additional information

• Is it possible to require manual approval for a specific job in GitHub Actions CI/CD? community/community#186436 asked if it was possible
• Is it possible to require manual approval for a specific job in GitHub Actions CI/CD? community/community#186436 (comment) explains that it's possible

1. Visit https://github.com/check-spelling-sandbox/super-duper-fishstick/settings/environments (or similar)
2. Click New environment (or similar)
3. Name it (for my example, I picked spelling)
4. Check Required reviewers
5. Fill in reviewers
   
6. Save
7. Update the workflow to include environment: as in https://github.com/check-spelling-sandbox/super-duper-fishstick/blob/1a6c62c10d1310abfeb58d5b15b73c57b2c768a3/.github/workflows/spelling.yml#L84

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1. When a workflow run is triggered, it will appear queued:
   
2. Clicking the workflow run will yield something like:
   
3. Clicking Review deployments yields an approval dialog:
   
4. Check the environment and then click Approve and deploy
5. The job will start running: