add staging environment and set as default build (for the static site)

src/Umbraco.Web.UI.Client/.env.production

@@ -1,4 +1,2 @@
-# Copy this to .env.local and change what you want to test.
 VITE_UMBRACO_INSTALL_STATUS=running # running or must-install or must-upgrade
-VITE_UMBRACO_INSTALL_PRECONFIGURED=false
 VITE_UMBRACO_USE_MSW=off

src/Umbraco.Web.UI.Client/.env.staging

@@ -0,0 +1,2 @@
+VITE_UMBRACO_INSTALL_STATUS=running # running or must-install or must-upgrade
+VITE_UMBRACO_USE_MSW=on

src/Umbraco.Web.UI.Client/package.json

@@ -17,7 +17,8 @@
   },
   "scripts": {
     "dev": "vite",
-    "build": "tsc && vite build",
+    "build": "tsc && vite build --mode staging",
+		"build:production": "tsc && vite build",
     "preview": "vite preview --open",
     "test": "web-test-runner --coverage",
     "test:watch": "web-test-runner --watch",