LibWeb: Dispatch pointer events to ::backdrop originating element

Author: https://github.com/Gingeh
Commit: 972547635f
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4263
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/CSS/PseudoElements.json

@@ -34,7 +34,8 @@
     "is-generated": true
   },
   "backdrop": {
-    "spec": "https://drafts.csswg.org/css-position-4/#selectordef-backdrop"
+    "spec": "https://drafts.csswg.org/css-position-4/#selectordef-backdrop",
+    "is-generated": true
   },
   "before": {
     "spec": "https://drafts.csswg.org/css-pseudo-4/#selectordef-before",