Adding android and ios icon resources.

android/app/src/main/AndroidManifest.xml

@@ -9,7 +9,7 @@
     <application
         android:name="io.flutter.app.FlutterApplication"
         android:label="botz_app"
-        android:icon="@mipmap/ic_launcher">
+        android:icon="@mipmap/launcher_icon">
         <activity
             android:name=".MainActivity"
             android:launchMode="singleTop"

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

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<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"/>
+</adaptive-icon>

android/app/src/main/res/values/colors.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="ic_launcher_background">#ffff00</color>
+</resources>