Fix: Fire events on elements with mousetrap class in Shadow Dom

[zastavnitskiy]

Hi!

I think I found a small issue with handling events in Shadow Dom.

Events from input elements with mousetrap class are not fired.

Fix seems pretty straightforward, I tested it in the browser and it works fine.

However, I can't get the unit test to work. Might have a look later, but feel free to edit this PR.

Hope this helps. And thank you — it's a great library!