Adding link to `rliable`?

[agarwl]

I was wondering if the open-source library rliable, corresponding to our NeurIPS 2021 best paper, for reliably evaluating reporting performance on ML and RL benchmarks, especially when using a handful of runs might be relevant for the README. Adding this as an issue as I wasn't sure though about the best place to add a link to this library in the README.