LibWeb: Update the select label when option's children are changed

Author: https://github.com/Gingeh
Commit: 58c78cb003
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3209
Reviewed-by: https://github.com/awesomekling

Libraries/LibWeb/HTML/HTMLOptionElement.h

@@ -52,8 +52,10 @@ private:
 
     virtual void inserted() override;
     virtual void removed_from(Node*) override;
+    virtual void children_changed() override;
 
     void ask_for_a_reset();
+    void update_selection_label();
 
     // https://html.spec.whatwg.org/multipage/form-elements.html#concept-option-selectedness
     bool m_selected { false };