add script to watch cms build

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

@@ -29,7 +29,8 @@
 		"dev": "vite",
 		"build": "tsc && vite build --mode staging",
 		"build:for:static": "tsc && vite build",
-		"build:for:backoffice": "tsc && vite build -c vite.element.config.ts",
+		"build:for:cms": "tsc && vite build -c vite.cms.config.ts",
+		"build:for:cms:watch": "npm run build:for:cms -- --watch",
 		"preview": "vite preview --open",
 		"test": "web-test-runner --coverage",
 		"test:watch": "web-test-runner --watch",