[suggestion] Add DCO bot to enforce Developer Certificate of Origin (DCO) on Pull Requests

[acch]

According to the contribution guidelines, all contributors are required to sign their commits. This is to document that they agree with the Developer Certificate of Origin (DCO).

A GitHub App is available to enforce the above. Once installed, this app will set the status to failed if commits in a Pull Request do not contain a valid Signed-off-by line.

→ https://github.com/apps/dco