PoC: [feature] Introduce TOML configuration file

[cmacrae]

Hi @Akatsuki-py! 👋

Thanks very much for PokéTraveler! 🙇 It's a really cool project! G/S/C have been my favourite games since I was a child 😁

About

I was playing around in the code a bit today and decided to add a bit of functionality.

These changes introduce the ability to configure the keyboard mapping and player appearance using a TOML file, like so:

avatar = 1

[controls]
up = "k"
down = "j"
left = "h"
right = "l"
start = "enter"
a = "a"
b = "s"

For discussion

I have marked this as as a draft, as these are just some initial ideas.
There is probably some quite opinionated terminology/choices (like chosing TOML, and the word avatar, etc.) and the code isn't quite ready/could certainly be better.

But, I thought it would be nice to share early so we can discuss your thoughts and see if you'd be interested in accepting this stuff up stream 🙃