themed icon support (#419)

Author: nvllz

app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,4 +1,5 @@
 <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>