## What are the changes about?
This PR adds a flake.nix and flake.lock to provide a reproducible development environment for ly using Nix.
The development shell provides the dependencies required to build ly:
- zig
- pam
- xcb
## What existing issue(s) does this resolve?
N/A
## Pre-requisites
- [x] I have tested & confirmed the changes work locally
- [x] I have read and fully adhere to the rules set in the contributing guidelines found in `CONTRIBUTING.md`
Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/1066
Reviewed-by: AnErrupTion <anerruption+codeberg@disroot.org>
