added xr reading

schedule-ugrad.md

@@ -145,6 +145,7 @@ Discussion of  accessibility testing and born accessible systems.
 - <i class="fa-solid fa-house-laptop" aria-hidden="true"/> Readings and Preparation:
   - Read [How Android Accessibility Services Can Be Used to Hack Your Phone](https://www.makeuseof.com/tag/android-accessibility-services-can-used-hack-phone/); Lewis et al. 
   - Read [Security and Privacy](https://bookish.press/tac/SecurityAndPrivacy) from "Teaching Accessible Computing"
+  - Read the WCAG [XR Access](https://www.w3.org/TR/xaur/) guidelines through Section 3.9
 
 {: .week}
 # Week 8 (11/10-11/16): Accessibility Across Technology