Checking homepage URLs

[purcell]

Hey! I noticed a couple of recently-added packages (eshell-atuin/lazy-ruff) ended up having invalid homepage tags (;; URL: headers), and I reckon we could automate checks for those, at least to make sure they're not 404. It probably isn't appropriate for package-lint to make spurious web requests, because I feel like that should work identically offline, so perhaps that check belongs here?

[riscy]

Hey :) I definitely think that goes here. I'll try this out right now -- thanks for the great suggestion.

[purcell]

Yay! Nice.