Suggest: add URL to this repo to rust doc

[Richèl Bilderbeek]

Dear chess maintainers, hi @jordanbray,

Thanks for the chess crate, I found it at the Rust docs at https://docs.rs/chess/3.2.0/chess/.

I did have to guess that the Rust docs are generated from this crate, which is the problem I suggest to solve: add a link to this GitHub repo in the documentation. In that way, any user can find the source code of the crate easily.

For me, I wanted to find the source code to see an example of how Rust is done properly. I think a chess game is of nice intermediate complexity :-)

I hope you will help out me and my fellow rustlings. Thanks and cheers, Richel Bilderbeek