Add links to repositories from the README for each crate

[nrc]

Either in the table or in each section or both (preferably both, and actually adding a link from the expanded section to the docs would be useful too). Apologies if there are links somewhere and I missed them.

[brson]

Thanks for the suggestion. While I understand the desire for direct access to those links I chose not to this time around because I wanted to drive the reader's attention to each crate's docs.rs page as the primary documentation. That page in turn has links to the repo, but you do have to dig.

I think that users shouldn't have to know any other resources besides docs.rs, although I admit that I usually go straight to the repo because I'm skeptical of the quality of any given crate's docs. Crate docs need to be better.