Easier showing/hiding of layers by dragging over eye icons

[bjorn]

To quote eishiya from the Tiled forum:

In Photoshop, I can quickly show/hide several layers by clicking on one visibility icon and dragging to others, and it’ll set their visibility to be the same:

I often try to do this in Tiled out of habit, but it drags the layer in the layer stack instead. It would be nice if Tiled had this same feature, or at least didn’t drag the layer if I click+drag on the eye or lock icons rather than the rest of the layer.

I totally agree the eyes should work like this. Also worth considering in combination with #1995.