Support cuda releases of Jax

[kamadorueda]

Seems it's only a matter of indexing this page:

https://storage.googleapis.com/jax-releases/jax_releases.html

pip install jax[cudaxx] means installing jaxlib+cudaxx from such index

https://github.com/google/jax/blob/9a5cf7c81e0e2cc39358574cdb5887397ec7557b/setup.py#L61

This introduces a nice feature into the project: indexing other repository APIs than PyPI