Adding support for observers

[BramVanroy]

I'm not sure if this is possible but as MDN suggests that observers behave very similarly to event listeners, it might be worth the shot. The MutationObserver is such an observer. It's really useful and cool (it observes a DOM element as the name implies), but from a bit of testing I found that it encounters a lot of changes which in turn trigger many callbacks. It would be nice to be able to throttle and even debounce these!