fix(Mac): horizontal scrolling when shift key is held

[KKishikawa]

Fixes #686

Description

When scrolling vertically while holding down the Shift key, the vertical scroll volume was converted to a horizontal scroll volume.
Since this process is handled at a higher level on MacOS, I fixed the problem so that no re-conversion is done.

[ProjectInfinity]

Sorry this is a little delayed, I want to test it before merging and I need to do some setup first before I am able to test it on macOS. I have not forgotten about it!

[ProjectInfinity]

Hi, I finally had a macOS setup to test on. Whilst holding shift and scrolling down (without) this patch it worked like it should. Is the issue only related to mice? On touchpad it worked fine whilst using shift.

[KKishikawa]

@ProjectInfinity
Thanks for the review.
Um, sorry, I'm not sure I understand what you're saying because I'm not very good at English.

The basis of this problem is to provide a way to scroll horizontally, since a typical mouse can only scroll vertically.
About the touchpad, Well, on a Mac, you can scroll horizontally by sliding two fingers sideways. So I don't think it's necessary to consider adding a way to scroll horizontally using the Shift key. What do you think about this?

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I have created a simple REPL that can confirm the "swapping".
https://svelte.dev/repl/9032f26c6d1a4f7fab9f1d6e96416079?version=3.49.0

I tested mouse scrolling in a windows environment and a Mac environment.
The result was that the value of the wheel event was swapped only when the mouse scrolled while holding down the Shift key on the Mac.
I have also tried scrolling with a touchpad on a Mac, but the "swapping" does not seem to happen.

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Windows 11 (23H2) Pro x64
Google Chrome 122.0.6261.71

mouse wheel

macOS Sonoma 14.3.1 (Apple M3 Pro)
Google Chrome 121.0.6167.184

mouse wheel

touchpad (without shift key)

scroll_normal.mov

touchpad (with shift key)

scroll_shift.mov