Validate DCoO PR signoff

[LostLuma]

Description

Automates check for PR authors having agreed to the last bullet point in the PR template.

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
  • I have updated the changelog with a quick recap of my changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)
• I have read and agree to the Developer Certificate of Origin for this contribution

[LostLuma]

Cool todo idea: Create an action in this repo that syncs all but the meta action to the other projects ...