add network permission for android

android/app/src/main/AndroidManifest.xml

@@ -5,6 +5,7 @@
          In most cases you can leave this as-is, but you if you want to provide
          additional functionality it is fine to subclass or reimplement
          FlutterApplication and put your custom class here. -->
+    <uses-permission android:name="android.permission.INTERNET" />
     <application
         android:name="io.flutter.app.FlutterApplication"
         android:label="lemmur"