Swipe implementation

[JayPanoz]

Currently there is no swipe listener in EPUBNavigatorListeners, while it could be useful for app developers i.e. setting an immersive mode/hiding the UI when swiping.

It’s not as easy as handling a callback though, since a swipe event could then fire without the position changing for instance, which isı't necessarily what may be expected. We need to define what a swipe event is, and what it should cover.

Note there are talks about redesigning these so that they work in a way similar to adding/removing event listeners happening in parallel.

[JayPanoz]

Implementation detail to keep in mind: ColumnSnapper has a 150ms bounce animation that has to be taken into account as it can lead to edge cases – encountered an edge case yesterday in Playground that is admittedly very specific to Playground i.e. mounting/unmounting scroll affordances in the absence of Injection API, with the current iframe failing to unhide on navigation but only when using swiping to navigate, taps were OK.