Issue building proc-macro2 dependency on nightly

[dnlmlr]

Hi! I can see that this repo hasn't been updated in about 5 years and want to start with saying that is is totally fine.

But in case you want to keep this in working condition, I just ran into an issue with the proc-macro2 dependency when building on current nightly rust. From what I've gathered by skimming through the referenced issue, it seems like a simple dependency version bump should fix that.

Not sure what is going on with the code in this repo vs the crates.io version, there seems to be some kind of desync there, but it would be really cool if you have a way to push an update with the bumped version. If not that's fine too, no problem

[dnlmlr]

Sorry I just realized that the current code iteration is in the https://github.com/gobanos/cargo-aoc mono repo.

Anyways, it seems like the crates.io repo link still references this repo which you might want to change. Also if this is indead no longer active, I would suggest thinking about archiving the repo