Enable Developer Certificate of Origin (DCO) for Chisel Repositories

[bensternthal]

Description

As part of the LF project onboarding cleanup, our Project Formation Team has recommended implementing a Developer Certificate of Origin (DCO) across the Chisel repositories (and other CHIPS projects).

The DCO ensures that all code contributions are signed off, verifying that contributors agree to the terms of open-source development. This helps maintain compliance and transparency in our repositories.

Task

Enable the DCO GitHub App on Chisel repositories using Probot DCO.

@jackkoenig for visibility and possibly implementation.