Recommend prettier extension in vscode workspace

Author: aomarks

lit-dev.code-workspace

@@ -13,5 +13,13 @@
 			"path": "."
 		}
 	],
-	"settings": {}
+	"settings": {
+		"files.insertFinalNewline": true,
+		"files.trimTrailingWhitespace": true,
+	},
+	"extensions": {
+		"recommendations": [
+			"esbenp.prettier-vscode",
+		]
+	}
 }