Set up and configure neotest

[99linesofcode]

An extensible framework for interacting with tests within NeoVim.

Already has a plugin for nixvim, just need to implement and configure it. Once again, I'll steal the keybindings from Lazyvim

https://nix-community.github.io/nixvim/plugins/neotest/index.html
https://github.com/nvim-neotest/neotest
https://github.com/V13Axel/neotest-pest
https://github.com/LazyVim/LazyVim/blob/c64a61734fc9d45470a72603395c02137802bc6f/lua/lazyvim/plugins/extras/test/core.lua