Add woodpecker CI pipeline status badge — radicle-desktop

Since we now have all the current tests on woodpecker, I think it would be nice to have a status badge on the README.md

 # Radicle Desktop
 [![status-badge](https://woodpecker.radworks.garden/api/badges/6/status.svg)](https://woodpecker.radworks.garden/repos/6)
 This desktop application lets you interact with [Radicle][rad], a peer-to-peer code collaboration and publishing stack.
 ## Installation