Add swipe/slide/zoom functionality

[rejas]

From "paxperscientiam": On the UX side of things, the ability to slide over to the next image via trackpad or mobile screen, would be great. To this end, I think we want a sliding motion to be equivalent to pressing left/right buttons, correct?"

Correct :-)

[paxperscientiam]

@rejas Just for the record, there is no interest in adding dependencies, correct?

[rejas]

No, only if it was very very small. For exmaple issue #47 would be really easy to fix if I would use hammer.js but then the size of the library doubles....

[paxperscientiam]

@rejas just to update, mobile finger sliding works just fine. It's only trackpad that does not.

[rejas]

Trackpads? Well, for those that want to add support for that, they could use their own library for detecting that an call a function for next / prev on our library. what do you think?

[denalena]

@rejas just to update, mobile finger sliding works just fine. It's only trackpad that does not.

For me zooming doesn't work on Pixel XL with Android 9 and Chrome 86.0.4240.198

Do you have to configure it the right way to work? Or did you mean sliding next/prev and not zooming?