Add option to select

        :param value: The value that the option represent.

        :param text: The text that should be displayer in dropdown

        :param selected: True if the option should be the default value.

def add_option(self, value, text, selected=False):
        """
        Add option to select

        :param value: The value that the option represent.

        :param text: The text that should be displayer in dropdown

        :param selected: True if the option should be the default value.
        """
        option = {"value": value, "text": text, "selected":selected}
        self.options += [option]
        if selected:
            self.selected_options += [option]
            self._value.append(value)
            if self._persist_value:
                self.settings.store_value("selected_options", self.selected_options)