android: use better icons

vector assets are available
unfortunately android studio mutilates citra's vector icon

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

@@ -15,12 +15,12 @@
 
     <application
         android:name="org.citra_emu.citra.CitraApplication"
-        android:label="Citra Emulator"
+        android:label="Citra"
-        android:icon="@drawable/ic_citra"
+        android:icon="@mipmap/ic_citra"
         android:allowBackup="true"
         android:supportsRtl="true"
         android:isGame="true"
-        android:banner="@drawable/ic_citra">
+        android:banner="@mipmap/ic_citra">
 
         <activity
             android:name=".ui.main.MainActivity"

src/android/app/src/main/res/drawable/ic_add.xml

@@ -0,0 +1,5 @@
+<vector android:height="24dp" android:tint="#FFFFFF"
+    android:viewportHeight="24.0" android:viewportWidth="24.0"
+    android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="#FF000000" android:pathData="M19,13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/>
+</vector>

src/android/app/src/main/res/mipmap-anydpi-v26/ic_citra.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="@mipmap/ic_launcher_foreground"/>
+</adaptive-icon>

src/android/app/src/main/res/mipmap-anydpi-v26/ic_citra_round.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="@mipmap/ic_launcher_foreground"/>
+</adaptive-icon>

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

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