[ThemePicker 7/N] Initial setup of ThemeFragment UI

Add a view for the theme preview card for font, and hook up
the option tiles as well.

Bug: 120559294

Change-Id: I7efa779e9db730f8aaff151eac65bee42ed5db6b
diff --git a/res/layout/fragment_theme_picker.xml b/res/layout/fragment_theme_picker.xml
index 95702f1..0fd4044 100644
--- a/res/layout/fragment_theme_picker.xml
+++ b/res/layout/fragment_theme_picker.xml
@@ -22,7 +22,12 @@
     android:background="@color/category_picker_background_color">
     <include layout="@layout/section_header"/>
 
-    <!-- TODO(santie): Preview pager goes here... -->
+    <com.android.customization.widget.PreviewPager
+        android:id="@+id/theme_preview_pager"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_weight="1"
+        android:background="@color/secondary_color"/>
 
     <LinearLayout
         android:id="@+id/options_section"