Investigate Crystal support

[JoshuaKGoldberg]

https://crystal-lang.org/

Crystal’s syntax is heavily inspired by Ruby’s, so it feels natural to read and easy to write, and has the added benefit of a lower learning curve for experienced Ruby devs.
Crystal is statically type checked, so any type errors will be caught early by the compiler rather than fail on runtime. Moreover, and to keep the language clean, Crystal has built-in type inference, so most type annotations are unneeded.

Looks snazzy!