docs: break out as contributing section

Author: l-monninger

README.md

@@ -4,6 +4,8 @@
 
 Movement Labs' Fast Finality Settlement is a proof of stake settlement system. 
 
+## Contributing
+
 | Task | Description |
 |------|-------------|
 | [Upcoming Events](https://github.com/movementlabsxyz/ffs/issues?q=is%3Aissue%20state%3Aopen%20label%3Apriority%3Ahigh%2Cpriority%3Amedium%20label%3Aevent) | High-priority `event` issues with planned completion dates. |