_defineOverlayConfig() {
      return {
        ...super._defineOverlayConfig(),
        placementMode: 'local',
        popperConfig: {
          ...super._defineOverlayConfig().popperConfig,
          placement: 'bottom',
        },
      };
    }
@overridable method `_defineOverlay`
@desc Overrides arrow and keepTogether modifier to be enabled,
and adds onCreate and onUpdate hooks to sync from popper state
@returns {import('../types/OverlayConfig.js').OverlayConfig}