Add help url placeholders for new pages

Bug: 38412798
Test: visual
Change-Id: I4ede523cb13790ea05309279f80a778b2086f850

src/com/android/settings/gestures/DoubleTapScreenSettings.java

@@ -52,6 +52,11 @@ public class DoubleTapScreenSettings extends DashboardFragment {
         return R.xml.double_tap_screen_settings;
     }
 
+    @Override
+    protected int getHelpResource() {
+        return R.string.help_url_double_tap_screen;
+    }
+
     @Override
     protected List<PreferenceController> getPreferenceControllers(Context context) {
         return buildPreferenceControllers(context, getLifecycle());