Add Nix flake and improve derivation

This adds a Nix flake to the repo as well as updates the derivation so
that it includes `lzip` as a dependency

flake.nix

@@ -0,0 +1,21 @@
+{
+  description = "Waydroid Extras Script";
+  inputs = {
+    systems.url = "github:nix-systems/default";
+  };
+  outputs = { self, nixpkgs, systems }:
+  let
+    inherit (nixpkgs) lib;
+    eachSystem = lib.genAttrs (import systems);
+    mkApp = program: { type = "app"; inherit program; };
+  in {
+    packages = eachSystem (system: rec {
+      waydroid_script = nixpkgs.legacyPackages."${system}".callPackage ./package.nix { };
+      default = waydroid_script;
+    });
+    apps = eachSystem (system: rec {
+      waydroid_script = mkApp "${self.outputs.packages.${system}.waydroid_script}/bin/waydroid_script";
+      default = waydroid_script;
+    });
+  };
+}