Added button to layout.

Author: ashryanbeats

asset-browser-ui/app/src/main/res/layout/content_main.xml

@@ -12,8 +12,11 @@
     tools:context="com.adobe.assetbrowserui.MainActivity"
     tools:showIn="@layout/activity_main">
 
-    <TextView
-        android:layout_width="wrap_content"
+    <Button
+        android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:text="Hello World!" />
+        android:text="View Creative Cloud Assets"
+        android:id="@+id/launchAssetBrowserButton"
+        android:layout_alignParentTop="true"
+        android:layout_centerHorizontal="true" />
 </RelativeLayout>