update contributor's guide

Author: RobinHankin

CONTRIBUTING.md

@@ -9,12 +9,9 @@ welcome:
 - **Bug Reports**: Feel free to report any bugs you encounter.
 - **Documentation**: Typos, clarity issues, or missing guides: your
   help is welcome here.
+- **Use cases**: if you use `weyl`, tell me about it!  I want to
+  know how the software is being used!
 - **Feature Discussions/Requests**: Got an idea? Open an issue to
   discuss its potential.
 - **Code Contributions**: All code contributions are welcome.
 
-
-Tests and checks are run on the CI, however locally one can use:
-`devtools::test()`.  Ideally each change should be documented.  Major
-changes should be `vignettes`.
-