Userland: Add horizontal mouse scroll support

Author: https://github.com/can3p
Commit: 1662213737
Pull-request: https://github.com/SerenityOS/serenity/pull/11246
Reviewed-by: https://github.com/kleinesfilmroellchen ✅

Userland/Applications/PDFViewer/PDFViewer.cpp

@@ -75,7 +75,7 @@ void PDFViewer::mousewheel_event(GUI::MouseEvent& event)
     if (!m_document)
         return;
 
-    bool scrolled_down = event.wheel_delta() > 0;
+    bool scrolled_down = event.wheel_delta_y() > 0;
 
     if (event.ctrl()) {
         if (scrolled_down) {