feat: add touch support

[TimP4w]

Resolves #353

[TimP4w]

I had a better look. Scrolling wouldn't work with this.

Apparently St.ScrollView does not support touch dragging? Not exactly sure, but i created a minimal example with only a St.ScrollView and it didn't scroll on touch.

So I guess I have to implement it myself. This makes the whole thing less trivial, because now we need to check if it's a tap or a drag, then selectively either propagate or block the event and finally move the scroll by deltaY if it was a drag.

[domferr]

Hey, thank you so much for your contribution! I have little time to review, but It will be my top priority <3

[domferr]

Changed base branch to v17.1 to aim to get this feature in the upcoming release!

[domferr]

Great work, thank you! I have refactored the code, ensuring it works on GNOME versions from 42 to 49. I also improved the strategy, by reacting to touch events instead of emitting button press event (which was failing on GNOME 44).

Unfortunately I cannot test the scrolling on my GNOME 44, since scrollView.vadjustment is not available. If I test with a virtual machine, touch events are propagated as button press/release events and I cannot test properly

[domferr]

@TimP4w I will merge this PR, however can you double check everything is working on your side? Thank you!

[TimP4w]

@domferr I'm a bit busy at the moment, but I'll try to test it on my laptop by the end of the week (GNOME 48)

[domferr]

Thank you @TimP4w !