Updated _Sidebar (markdown)

_Sidebar.md

@@ -17,6 +17,7 @@
 * [Working on Raspberry Pi](Working-on-Raspberry-Pi)
 * [Working for Android](Working-for-Android)
 * [Working for Web (HTML5)](Working-for-Web-(HTML5))
+* [Working for UWP (Universal Window Platform)](Working-for-UWP)
 
 ## Misc Help
 * [How To: Using SpriteFonts](Using-BMFonts)