feat: add a home-manager example configuration

This adds a home-manager example configuration to ensure the
home-manager standalone module works properly.

flake-modules/example-configs.nix

@@ -0,0 +1,33 @@
+{ inputs, lib, ... }:
+{
+  flake = {
+    # Example vm configuration
+    nixosConfigurations.vm = lib.nixosSystem {
+      modules = [
+        inputs.self.nixosModules.default
+        ../example-vm # import vm configuration
+        {
+          nixpkgs = {
+            overlays = builtins.attrValues inputs.self.overlays;
+            config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [ "steam-unwrapped" ];
+          };
+          # pin nixpkgs to the one used by the system
+          nix.registry.nixpkgs.flake = inputs.nixpkgs;
+        }
+      ];
+    };
+    homeConfigurations.example = inputs.home-manager.lib.homeManagerConfiguration {
+      pkgs = inputs.nixpkgs.legacyPackages.x86_64-linux;
+      modules = [
+        inputs.self.homeModules.standalone
+        ../example-hm/home.nix # import home-manager configuration
+        {
+          nixpkgs.overlays = [
+            inputs.self.overlays.unstable
+            inputs.lix-module.overlays.default
+          ];
+        }
+      ];
+    };
+  };
+}