[Suggestion] Readme links should point to code, and ref should be separated

I believe the README.md should be a place to showcase what the code can do.
Why not using the links to bring users to the place where the features are coded (or to the doc) and put the reference next to it?

e.g. something like this:

[UCB1](https://github.com/facebookresearch/ReAgent/blob/main/reagent/mab/ucb.py#L58-L78) [(doc)](https://reagent.ai/api/reagent.mab.html?highlight=ucb1#reagent.mab.ucb.UCB1) [(ref)](https://www.cs.bham.ac.uk/internal/courses/robotics/lectures/ucb1.pdf)