Warn about built-in script limitations in the script creation dialog

This partially addresses #31758.

(cherry picked from commit ac210e196c7775a4b8955ad74b77e9ff017cae36)

editor/script_create_dialog.cpp

@@ -687,6 +687,8 @@ void ScriptCreateDialog::_update_dialog() {
 
 	// Is Script created or loaded from existing file?
 
+	builtin_warning_label->set_visible(is_built_in);
+
 	if (is_built_in) {
 		get_ok()->set_text(TTR("Create"));
 		parent_name->set_editable(true);
@@ -765,6 +767,13 @@ ScriptCreateDialog::ScriptCreateDialog() {
 	path_error_label = memnew(Label);
 	vb->add_child(path_error_label);
 
+	builtin_warning_label = memnew(Label);
+	builtin_warning_label->set_text(
+			TTR("Note: Built-in scripts have some limitations and can't be edited using an external editor."));
+	vb->add_child(builtin_warning_label);
+	builtin_warning_label->set_autowrap(true);
+	builtin_warning_label->hide();
+
 	status_panel = memnew(PanelContainer);
 	status_panel->set_h_size_flags(Control::SIZE_FILL);
 	status_panel->add_child(vb);

editor/script_create_dialog.h

@@ -48,6 +48,7 @@ class ScriptCreateDialog : public ConfirmationDialog {
 	LineEdit *class_name;
 	Label *error_label;
 	Label *path_error_label;
+	Label *builtin_warning_label;
 	PanelContainer *status_panel;
 	LineEdit *parent_name;
 	Button *parent_browse_button;