maint: add automation for merging of auto PRs

[mcdurdin]

The following websites need automation of auto PRs and related tweaks:

• api.keyman.com
  • add auto-approve-and-merge-keyman-server-pr.yml --> maint: add auto approve action api.keyman.com#296
  • check branch protection - required status checks - on master branch
  • add branch protection - required status checks - on staging branch
• help.keyman.com
  • add branch protection - required status checks - on staging branch
• keyman.com
  • add auto-approve-and-merge-keyman-server-pr.yml --> maint: add auto approve action #602
  • check branch protection - required status checks - on master branch
  • add branch protection - required status checks - on staging branch
• keymanweb.com
  • add auto-approve-and-merge-keyman-server-pr.yml --> maint: add auto approve action keymanweb.com#162
  • check branch protection - required status checks - on master branch
  • add branch protection - required status checks - on staging branch
• s.keyman.com
  • add branch protection - required status checks - on staging branch
• website-local-proxy
  • add auto-approve-and-merge-keyman-server-pr.yml --> maint: add auto approve action website-local-proxy#18
  • check branch protection - required status checks - on master branch (no checks currently on this repo)

Once these are in place, we can enable auto-merge for staging refresh PRs in the management repo.