Add microdroid demo app

Add a demo app showing how an app can start a VM.

Bug: N/A
Test: TARGET_BUILD_APPS=MicrodroidDemoApp m apps_only dist
adb install out/dist/MicrodroidDemoApp.apk
adb push out/dist/MicrodroidDemoApp.apk.idsig /data/local/tmp/virt/
adb root
adb shell start virtualizationservice
<then launch the app>

Change-Id: If46b2f8910b98b2b29ca0c629e1f7eacc01a477a
diff --git a/demo/res/layout/activity_main.xml b/demo/res/layout/activity_main.xml
new file mode 100644
index 0000000..026382f
--- /dev/null
+++ b/demo/res/layout/activity_main.xml
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="#FFC107"
+    android:scrollbars="horizontal|vertical"
+    android:textAlignment="textStart"
+    tools:context=".MainActivity">
+
+    <ScrollView
+        android:id="@+id/scrollview"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent">
+
+        <TextView
+            android:id="@+id/textview"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:background="#FFEB3B"
+            android:fontFamily="monospace"
+            android:textColor="#000000" />
+    </ScrollView>
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/demo/res/values/colors.xml b/demo/res/values/colors.xml
new file mode 100644
index 0000000..f8c6127
--- /dev/null
+++ b/demo/res/values/colors.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="purple_200">#FFBB86FC</color>
+    <color name="purple_500">#FF6200EE</color>
+    <color name="purple_700">#FF3700B3</color>
+    <color name="teal_200">#FF03DAC5</color>
+    <color name="teal_700">#FF018786</color>
+    <color name="black">#FF000000</color>
+    <color name="white">#FFFFFFFF</color>
+</resources>
\ No newline at end of file
diff --git a/demo/res/values/themes.xml b/demo/res/values/themes.xml
new file mode 100644
index 0000000..16b8ab3
--- /dev/null
+++ b/demo/res/values/themes.xml
@@ -0,0 +1,16 @@
+<resources xmlns:tools="http://schemas.android.com/tools">
+    <!-- Base application theme. -->
+    <style name="Theme.MicrodroidDemo" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+        <!-- Primary brand color. -->
+        <item name="colorPrimary">@color/purple_500</item>
+        <item name="colorPrimaryVariant">@color/purple_700</item>
+        <item name="colorOnPrimary">@color/white</item>
+        <!-- Secondary brand color. -->
+        <item name="colorSecondary">@color/teal_200</item>
+        <item name="colorSecondaryVariant">@color/teal_700</item>
+        <item name="colorOnSecondary">@color/black</item>
+        <!-- Status bar color. -->
+        <item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
+        <!-- Customize your theme here. -->
+    </style>
+</resources>