add firefox-mod-blur theme

pkgs/default.nix

@@ -1,4 +1,5 @@
 {pkgs, ...}: {
   nvchad = pkgs.callPackage ./nvchad {};
   astronvim = pkgs.callPackage ./astronvim {};
+  firefox-mod-blur = pkgs.callPackage ./firefox-mod-blur {};
 }

pkgs/firefox-mod-blur/default.nix

@@ -0,0 +1,28 @@
+{
+  lib,
+  stdenv,
+  pkgs,
+}:
+stdenv.mkDerivation {
+  pname = "firefox-mod-blur";
+  version = "v2.7.6";
+
+  src = pkgs.fetchFromGitHub {
+    owner = "datguypiko";
+    repo = "Firefox-Mod-Blur";
+    rev = "refs/heads/master";
+    sha256 = "sha256-9dPL+pVnOsAxzFWRjSk+RSe+x/CKQk3iQAyQDBrVE9U=";
+  };
+
+  installPhase = ''
+    mkdir $out
+    cp -r * "$out/"
+  '';
+
+  meta = with lib; {
+    description = "Firefox Mod Blur";
+    homepage = "https://github.com/datguypiko/Firefox-Mod-Blur";
+    platforms = platforms.all;
+    license = licenses.gpl3;
+  };
+}