Implement panning with touchpad and/or scroll-wheel

[emilk]

• Map is displaying and reacting to input correctly, both natively and on the web.
• CHANGELOG.md was updated with relevant information (or the change was purely internal).
• Closes Can't pan with 2D scroll #210

[abey79]

@podusowski it would be great if you could push a release after this one 🙏🏻

[podusowski]

0.28.0 is live.

[ForsakenHarmony]

I don't understand this change, why should the scroll-wheel pan?
IMO it should zoom by default like every other map, the mouse wheel panning is very confusing right now

[podusowski]

I think this arrangement comes from egui / winit stack. Zoom event exists too, through on native platforms and web it is triggered by ctrl-wheel. On Android, where I mainly use Walkers, it works by two-finger zoom gesture as expected, so I haven't put much thought on this. I suppose we could make it configurable.

[emilk]

I would love it if scrolling on a mouse would zoom, and two-finger-pan on a touch-pad would pan. Unfortunately they produce the same "Scroll" event, so it is difficult to distinguish what is what. There is a similar discussion here:

• Zoom without CTRL/CMD emilk/egui_plot#26

I'm sure there is some way to accomplish it, but will likely require some plumbing in egui. PRs welcome :)