Update README.md

Author: pioner92

README.md

@@ -41,7 +41,7 @@ apply from: project(':react-native-config-jsi').projectDir.getPath() + "/dotenv.
 ---
 
 ## 🚀 Usage
-
+> ⚠️ **Note:** After updating `.env`, rebuild or restart your app to apply changes.
 ```js
 import { RNConfig } from "react-native-config-jsi";