Put together an "intro to Rust" equivalent to our "intro to Go" in the prep

https://github.com/CodeYourFuture/immersive-go-course/tree/main/prep is very Go focused. Specifically:
* Tour of Go
* How to use the fmt package in Golang
* Go-focused intro to pointers
* Learn Go with tests
* Navigating Go documentation

We should add a Rust equivalent to "generally get to know the language".

I'm evaluating:
* https://google.github.io/comprehensive-rust/index.html (from Google)
* https://rust-exercises.com/01_intro/00_welcome (from Mainmatter)
* https://github.com/rust-lang/rustlings (from rust-lang)
* https://doc.rust-lang.org/book/ (from rust-lang)
* https://doc.rust-lang.org/rust-by-example/ (from rust-lang)

Key criteria are:
* Easy to generally pick up and follow
* Does pre-assume a lot of knowledge
* Explains terms (or references explanations) when first using them
* Introduces relevant sections of the language (e.g. we probably don't care much about unsafe, lifetimes, ffi, alloc golf). We probably do want async, but towards the end not the start.

Feel free to add more to both lists.