Expose event target

[tdammers]

There was already some commented-out code in place to expose the target of an event; I assume it was commented out because the type signature wants target to return a VNode, but it is unclear how to marshal the value back to a VNode. Personally, I believe that return value is wrong, because VNode is a virtual DOM node, but what we get from event.target is an actual DOM node, and the virtual-dom works, virtual → actual is one-way (or that's what I gathered).

Anyway, since marshalling from JS DOM nodes to VNode isn't very useful anyway IMO, I changed things such that the DOM node is just returned as-is, as a JSVal. This is obviously not typesafe, but other than that, it works, and allows me to pull properties out of the event target (in my particular use case, the value, which gets fed back into the reactive event loop on the Haskell side of things).

A proper solution would instead marshal to a properly typed something, but I figured that'd be a future improvement.