On touch devices every touch event should eventually result on a click
event, as explained
[here](https://developer.mozilla.org/en-US/docs/Web/API/Touch_events/Supporting_both_TouchEvent_and_MouseEvent#event_order).
However, this is not true for mobile Safari versions < 13 (2019).

Because we still rely on listening to touchstart events, we decided to
sandbox the shadow DOMs, by stopping the propagation of click and
touchstart at that level. This prevents the bubbling of these events
outside the shadow DOM and better isolates the pieces of the application
that should not interact with the host page.