fix(flake): utilize https://github.com/NixOS/nixpkgs/pull/454542 pending upstream merge
Add nixpkgs-bat-extras-pr input to override bat-extras package
in lairland configuration with the patched version from PR #454542.
Locked to commit 46e297cf987ef4fb1eb3b4eac1f978a4c2b80316 to protect
against force-pushes.
(This commit also includes an working draft of CONTRIBUTING.md, currently
unfinished but commited to version history anyway for checkpointing progress
before doing nixos-rebuild on my desktop machine.)
Co-authored-by: GitHub Copilot Chat <noreply@github.com>
Signed-off-by: Andrei Jiroh Halili <ajhalili2006@andreijiroh.dev>