Added JAX implementation of CFR

[kubicon]

Implementation of CFR that uses JAX. This allows running CFR with GPU acceleration. Speed up over python CFR implementation is ~10-times on CPU only.

The goal was to make it interchangable with the python CFR.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[lanctot]

Hi, thanks for the PR!

The reason the wheel tests are failing is because you need an empty init.py file in evert directory. Your new one is missing it. Can you add it?

(Don't forget the license header even if the file is empty .. e.g. just copy one of the other ones)

[kubicon]

Hey, I am sorry. Did not realize that init.py was important. However, it should be there now. Hopefully everything will work fine now