docs: Add nixpkgs link and repology badge to README

README.md

@@ -26,6 +26,12 @@ Features:
 ---
 
 ## Installation
+### Repositories
+[![Packaging status](https://repology.org/badge/vertical-allrepos/timewall.svg)](https://repology.org/project/timewall/versions)
+
+- Arch Linux (AUR): [timewall](https://aur.archlinux.org/packages/timewall) and [timewall-bin](https://aur.archlinux.org/packages/timewall-bin).
+- Nix: [timewall](https://search.nixos.org/packages?channel=unstable&show=timewall).
+
 ### Prerequisites
 `timewall` depends on [`libheif`](https://github.com/strukturag/libheif) for HEIF support, make sure you have it installed.
 If you're building it from source you may also need `libheif-dev`, depending on your distribution.