Allow click, doubleClick, and triggerEvent to trigger events on window.

[scalvert]

During a refactor that improved typings in this project, the getElement function was narrowed in what it would return - specifically it was correctly fixed to return elements, of which window is not. This had the side effect of removing support for triggering window events via triggerEvent, in addition to removing support for other helpers.

This PR restores that capability by adding a new getTarget util, which wraps the getElement util but additionally checks for the presence of window, and subsequently returns that in favor of an element.

TODO:

Update getElement calls in other helpers that are valid for window:

• triggerEvent
• click
• doubleClick

[rwjblue]

We should evaluate the other DOM helpers, see which should allow window (I think most should not so the default getElement behavior is fine for them).

[scalvert]

@rwjblue I did. It looks as though click and doubleClick are the only other ones that make sense with window. Updating the PR to include those.

[rwjblue]

You've labeled this as breaking, but how is it breaking? It seems that we are widening the types / allowed values (you can now do a thing you couldn't before), no?