Add new activity to AndroidManifest automatically

Author: ThexXTURBOXx

flutter_web_auth_2/android/src/main/AndroidManifest.xml

@@ -1,6 +1,11 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.linusu.flutter_web_auth_2">
 
+    <application>
+        <activity android:name="com.linusu.flutter_web_auth_2.AuthenticationManagementActivity">
+        </activity>
+    </application>
+
     <queries>
         <intent>
             <action android:name="android.support.customtabs.action.CustomTabsService" />