Arrows partially obscure click events to elements in the background

[evitolins]

Shepherd UI arrows have a partially-invisible footprint that can obscure items behind it from click events.

Adding pointer-events: none; to the arrow class would take care of the issue, and should cause no issues to the expected functionality.

[geekjuice]

I've updated the tether arrow mixin to configure the arrow's pointer event and set it to none for shepherd tours. Hopefully, no one actually expects the current behavior where the transparent area is actually block their click so I agree this should be the default behavior. 😸

You will probably need to update shepherd to version v1.1.1 which includes the tether v1, but it should continue to just work out of the box. Otherwise, feel free to just copy the stylesheets for now as you migrate over to the newer packages. Feel free to let me know if you run into any more issues.