Feature: support Home/End and maybe PageUp/Down

[J-Chris-Findlay-RESIDEO]

I really like how the KeyboardSensor works, but when I tried to override the coordinateGetter to in addition to the arrow events (which I just passed to sortableKeyboardCoordinates) when I added Home/End (and ^Home/^End) support, the resulting coords, when returned, get clamped such that they don't work, because the handler is assuming the event was only from an arrow press.

It'd be nice to handle this more internally, so this could work. Specifically, in my case - a grid sortable - Home/End go to the start/end of the current row, ^Home/^End go to the first/last spot, and I hadn't decided how PageUp/Down would move yet.

PS: consider keypad arrow support too, tho I'm not sure how to detect the current state of NumLock from JS yet.

I can supply the code I have so far if it helps, but don't currently have time to make a full PR.