LibWeb: Implement HTMLDialogElement::show()

Author: https://github.com/tcl3
Commit: 151cd11b5b
Pull-request: https://github.com/SerenityOS/serenity/pull/23188
Reviewed-by: https://github.com/trflynn89 ✅

Userland/Libraries/LibWeb/HTML/HTMLDialogElement.h

@@ -21,7 +21,7 @@ public:
     String return_value() const;
     void set_return_value(String);
 
-    void show();
+    WebIDL::ExceptionOr<void> show();
     void show_modal();
     void close(Optional<String> return_value);
 
@@ -35,6 +35,8 @@ private:
 
     void close_the_dialog(Optional<String> result);
 
+    void run_dialog_focusing_steps();
+
     String m_return_value;
 };