Support Zooming

[eric-lesslie]

I love this library and I'm using it in a project of mine, but I've been running into a little kink with what I'm trying to do with this photo editor.

It would be a cool feature to support zooming and panning for touch events for touchscreen enabled devices.

If this is aligned with the vision for the photo editor, I would be interested in making a PR with this change, since I'm already handling this locally.

[musama619]

@eric-lesslie Hey! Thanks a lot, really appreciate it 🙌

Panning does work with touch already, but you're right, pinch-to-zoom isn’t supported yet. If you have an improved version of the panning code, that’d be awesome to check out as well. Feel free to open a PR.