Add usesCleartextTraffic flag to playground application

required to run RN apps on Android 9 devices

playground/android/app/src/main/AndroidManifest.xml

-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-          package="com.reactnativenavigation.playground">
+<manifest xmlns:tools="http://schemas.android.com/tools"
+          package="com.reactnativenavigation.playground"
+          xmlns:android="http://schemas.android.com/apk/res/android">
 
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.READ_PHONE_STATE"/>
         android:allowBackup="false"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
-        android:theme="@style/AppTheme">
+        android:theme="@style/AppTheme"
+        android:usesCleartextTraffic="true"
+        tools:ignore="GoogleAppIndexingWarning">
         <activity
             android:name=".MainActivity"
             android:configChanges="orientation|screenSize|keyboard|keyboardHidden"
-            android:windowSoftInputMode="adjustResize"
             android:label="@string/app_name"
-            android:launchMode="singleTask">
+            android:launchMode="singleTask"
+            android:windowSoftInputMode="adjustResize">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>