feat: implement weatherWidgetFlag feature toggle using environment variable

Author: py-dev-nandini-12

src/app/flags.ts

@@ -0,0 +1,7 @@
+import { flag } from "flags/next";
+
+export const weatherWidgetFlag = flag<boolean>({
+  key: "weather-widget",
+  description: "Enable the weather widget for users.",
+  decide: () => process.env.WEATHER_WIDGET_ENABLED === "true",
+});