LibWeb: Add select and option collection set length

Author: https://github.com/bplaat
Commit: 5c277144d8
Pull-request: https://github.com/SerenityOS/serenity/pull/23895
Reviewed-by: https://github.com/shannonbooth

Userland/Libraries/LibWeb/HTML/HTMLOptionsCollection.h

@@ -9,6 +9,7 @@
 #include <AK/Variant.h>
 #include <LibWeb/DOM/HTMLCollection.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
+#include <LibWeb/WebIDL/Types.h>
 
 namespace Web::HTML {
 
@@ -23,6 +24,8 @@ public:
     [[nodiscard]] static JS::NonnullGCPtr<HTMLOptionsCollection> create(DOM::ParentNode& root, Function<bool(DOM::Element const&)> filter);
     virtual ~HTMLOptionsCollection() override;
 
+    WebIDL::ExceptionOr<void> set_length(WebIDL::UnsignedLong);
+
     WebIDL::ExceptionOr<void> add(HTMLOptionOrOptGroupElement element, Optional<HTMLElementOrElementIndex> before = {});
 
 private: