Update README to reflect current state

Author: gmarkall

README.md

@@ -1,22 +1,24 @@
 # Numba CUDA Target
 
-An out-of-tree CUDA target for Numba.
+The CUDA target for Numba. Please visit the [official
+documentation](https://nvidia.github.io/numba-cuda) to get started!
 
-This contains an entire copy of Numba's CUDA target (the `numba.cuda` module),
-and a mechanism to ensure the code from this module (`numba_cuda.numba.cuda`) is
-used as the `numba.cuda` module instead of the code from the `numba` package.
 
-This is presently in an early state and is published for testing and feedback.
+To report issues or file feature requests, please use the [issue
+tracker](https://github.com/NVIDIA/nvmath-python/issues).
 
-## Building / testing
+To raise questions or initiate discussions, please use the [Numba Discourse
+forum](https://numba.discourse.group).
+
+## Building from source
 
 Install as an editable install:
 
 ```
 pip install -e .
 ```
 
-Running tests:
+## Running tests
 
 ```
 python -m numba.runtests numba.cuda.tests