Make it easier to audit upgrades by diffing .crate files

[epage]

Recent supply-chain discussions had me thinking it could be helpful to see the differences in the published .crate file. There is currently a third-party tool for this but figured having it built directly in would raise awareness and make it easier to use.

A bonus is an idea I posted on the diff.rs issue tracker which is diffing across crates. This would help when looking at potential forks or supply chain attacks to figure out what was actually done (e.g. I just recently found clap_builder_cryo which didn't change the repository links, making it harder to figure out what was going on.