Add a link from the repo to the crate

[wiktor-k]

Hi,

I just found your crate and it looks really nice! If you don't mind I'll file a couple of smaller PRs in coming days.

Could you add the URL to the crate: https://crates.io/crates/z-base-32 in this repository's settings? (I think it's a cogwheel symbol to the right on the "Code" tab).

I think it makes it easy for others to go from the repo to the crate (just like crates.io has a back link to the repo).

Thanks for your time and such a great crate! 👏

[matusf]

Hi, thank you. Sure, go ahead.