Allow Zoom In / Zoom Out on other mappings [enhancement]

[philippedcote]

Description

I would to be able to zoom in or out as a gesture rather than using the scroll wheel.

Rationale

Like the zooming gesture on the trackpad, I would also like to be able to zoom in or out using a button and a gesture, instead of having to use the scroll wheel. It feels more natural.

For example, the zoom in gesture could be dragging the mouse toward the screen. Zoom out could be the opposite.

Additional info

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