add a widget that shows running builds

[moul]

"running builds" should:

• be always visible on the default view (unless explicitly disabled)
  • even if they don't have artifacts at all (not only artifact_kinds)
• have less info, less margin too, they are only here to show that there are some stuff in progress and that you should wait a little bit more or read the logs while it's building:
  • you can try to create a unique block with all the "running builds" and minimal info, including the PR ID, the title, the commit hash, a link to the build logs, and the author

I won't change the current API, you need to do an additional call to this endpoint: https://yolo.berty.io/api/build-list?build_state=1

[moul]

moved to #2