feat: scripts

[kilpatty]

It's been a minute since I've been in this project updating it, and now just coming back to it I find that I have forgotten a handful of tools that I used to check things.

e.g. I'm not quite sure how I previously found the MSRV, but now I have found a tool that does it quite eloquently: https://github.com/foresterre/cargo-msrv

Having some scripts that make things a lot easier to run (And not forget) would be wonderful for long-term development.

Take a look at the usual suspects again... Justfile, Makefile, cargo make etc.