PageSpeed Insights recommends using passive flag for touch event listeners

In diagnostic section in PageSpeed for [page](http://kod.djpw.cz/lfld-) with Flickity 2.3.0
https://pagespeed.web.dev/analysis/http-kod-djpw-cz-lfld-/640hzu4fjs?form_factor=mobile
is
_Does not use passive listeners to improve scrolling performance_
_Consider marking your touch and wheel event listeners as passive to improve your page's scroll performance. [Learn more about adopting passive event listeners](https://developer.chrome.com/docs/lighthouse/best-practices/uses-passive-event-listeners/?utm_source=lighthouse&utm_medium=lr)._

I don't know if it is enough to replace in the library this row
`elem[ bindMethod ]( startEvent, this );`
by
`elem[ bindMethod ]( startEvent, this, /^(touch|wheel)/.test(startEvent) ? { passive : true } : false );`

Passive support should also be [detected](https://github.com/WICG/EventListenerOptions/blob/gh-pages/explainer.md#feature-detection) for old browsers.

Start by locating the event-binding row containing `elem[ bindMethod ]( startEvent, this );` and read how `startEvent` is chosen. Review the linked passive-listener feature-detection guidance and check the browser support assumptions. Done means touch and wheel listeners use passive options where supported without breaking older browsers or Flickity interaction.

Written by the indexing model from the issue text.