feat: added ctrl key modifier to move pixels and selections by 10

[IArnaut2]

I have added the CTRL key as a modifier to move pixels and selections by 10.

• Created a coefficient that changes if the CTRL key is pressed.
• Replaced the offsets with the coefficient.

double coeff = e.IsControlPressed ? 10.0 : 1.0;

switch (e.Key.Value) {
	case Gdk.Constants.KEY_Left:
		dx = -coeff;
		break;
	// ...
}

The issues that might be not related are icons of some tools being small and the cursor disappearing in the canvas when hovering over the canvas while the Move Selected Pixels is active.

[cameronwhite]

This is related to #1559 so I'll ask for @pedropaulosuzuki to review :)
The change seems reasonable to me and feels separate from any additional shortcuts for custom translation offsets, since I don't think those would remove the arrow key option?

[pedropaulosuzuki]

This is related to #1559 so I'll ask for @pedropaulosuzuki to review :)

Looks good to me!

The change seems reasonable to me and feels separate from any additional shortcuts for custom translation offsets, since I don't think those would remove the arrow key option?

Agreed, we can have both systems at the same time.

[cameronwhite]

Thanks for the contribution! 🎉