LibJSGCVerifier: Detect missing JS_CELL() calls

Author: https://github.com/mattco98
Commit: abb4b6d117
Pull-request: https://github.com/SerenityOS/serenity/pull/23878
Issue: https://github.com/SerenityOS/serenity/issues/23805
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/HTML/DecodedImageData.h

@@ -15,6 +15,8 @@ namespace Web::HTML {
 
 // https://html.spec.whatwg.org/multipage/images.html#img-req-data
 class DecodedImageData : public JS::Cell {
+    JS_CELL(DecodedImageData, JS::Cell);
+
 public:
     virtual ~DecodedImageData();