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/AndroidManifest.xml b/demo/AndroidManifest.xml
new file mode 100644
index 0000000..ae4f734
--- /dev/null
+++ b/demo/AndroidManifest.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.android.microdroid.demo">
+
+    <application
+        android:label="MicrodroidDemo"
+        android:theme="@style/Theme.MicrodroidDemo">
+        <uses-library android:name="android.system.virtualmachine" android:required="true" />
+        <activity android:name=".MainActivity" android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>