icon: add regular png icon for compatibility with some launchers

See https://github.com/termux/termux-app/issues/991.

Adaptive icon will continue to be automatically used if supported.

app/src/main/AndroidManifest.xml

@@ -11,7 +11,7 @@
     <permission android:name="com.termux.permission.RUN_COMMAND"
         android:label="@string/run_command_permission_label"
         android:description="@string/run_command_permission_description"
-        android:icon="@drawable/ic_launcher"
+        android:icon="@mipmap/ic_launcher"
         android:protectionLevel="dangerous" />
 
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
@@ -28,7 +28,8 @@
     <application
         android:extractNativeLibs="true"
         android:allowBackup="false"
-        android:icon="@drawable/ic_launcher"
+        android:icon="@mipmap/ic_launcher"
+        android:roundIcon="@mipmap/ic_launcher_round"
         android:banner="@drawable/banner"
         android:label="@string/application_name"
         android:theme="@style/Theme.Termux"

app/src/main/res/drawable/ic_launcher.xml

@@ -1,34 +0,0 @@
-<vector xmlns:android="http://schemas.android.com/apk/res/android"
-    android:height="108dp"
-    android:width="108dp"
-    android:viewportWidth="108"
-    android:viewportHeight="108">
-
-    <path
-        android:fillColor="#000000"
-        android:pathData="M18,54
-                          A36,36 0 1,1 90,54
-                          A36,36 0 1,1 18,54 Z" />
-
-    <!-- Keep in sync with adaptive ic_foreground.xml: -->
-    <path
-        android:fillColor="#FFFFFF"
-        android:pathData="M34,38
-                          h6
-                          l12,16
-                          l-12,16
-                          h-6
-                          l12,-16
-                          "
-        />
-
-    <path
-        android:fillColor="#FFFFFF"
-        android:pathData="M56,66
-                          h18
-                          v4
-                          h-18
-                          "
-        />
-
-</vector>

app/src/main/res/mipmap-anydpi-v26/ic_launcher_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="@android:color/black"/>
+    <foreground android:drawable="@drawable/ic_foreground"/>
+</adaptive-icon>