feat: monochrome icon + predictive back gesture (#591)

* Add monochrome icon

* Enable predictive back gesture

* feat: monochrome icon + predictive back gesture

android/app/src/main/AndroidManifest.xml

@@ -17,7 +17,8 @@
         android:name="${applicationName}"
         android:icon="@mipmap/ic_launcher"
         android:largeHeap="true"
-        android:extractNativeLibs="true">
+        android:extractNativeLibs="true"
+        android:enableOnBackInvokedCallback="true">
         <activity
             android:name=".MainActivity"
             android:exported="true"
@@ -28,8 +29,7 @@
             android:windowSoftInputMode="adjustResize">
             <meta-data
               android:name="io.flutter.embedding.android.NormalTheme"
-              android:resource="@style/NormalTheme"
-              />
+              android:resource="@style/NormalTheme"/>
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>

android/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -2,4 +2,5 @@
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
   <background android:drawable="@color/ic_launcher_background"/>
   <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+  <monochrome android:drawable="@drawable/ic_launcher_foreground"/>
 </adaptive-icon>