LifetimeKata: A Practical Introduction to Lifetime Annotations, like Rustlings&MacroKata

A new project that's a follow-up to my MacroKata book, this walks through why lifetimes exist and how to write functions that use them:

https://tfpk.github.io/lifetimekata/ and https://github.com/tfpk/lifetimekata

It hasn't been fully peer-reviewed yet, so I'd love feedback/PRs!