This change implements pinch / magnification gesture handling.

This uses the following wayland
[protocol](https://wayland.app/protocols/pointer-gestures-unstable-v1).
And the following
[API](https://developer.apple.com/documentation/appkit/nsevent/magnification)
for mac.

- Original: https://github.com/gpui-ce/gpui-ce/pull/11

Release Notes:

- Zooming works with pinching in and out inside Image Viewer