Add an option to disable focus on click

[EugeneDae]

This is a follow-up to #111.

Focusing may be the right thing to do by all standards, but I think most people will agree that the behaviour depicted in the GIF is counterintuitive and confusing.

Please add an option to disable it.

[nvartolomei]

@EugeneDae http://flickity.metafizzy.co/options.html#accessibility set this to false.

[desandro]

@nvartolomei has it. Set accessibility: false. Which is not recommended. Again, from #76 (comment)

This behavior is actually a feature of keyboard accessibility. By clicking/tapping on a gallery, it adds focus to its element. This will jump the scroll so that element is completely in the viewport.

If this behavior is really bugging you, you can disable it with accessibility: false -- which I don't recommend because accessibility is a wonderful thing.