Holding backspace on iOS should delete words

[jaaberg]

When you have something typed on an iPhone and you hold the backspace, you expect it to start slowly deleting one and one character, then one and one word, and so on. But when it should be deleting words, it slows down the deletion of one and one character, so it actually deletes slower.

(I'm sorry i'm not able to provide a gif right now)
(Tested on iPhone 6 on both Chrome and Safari)

[hellendag]

I believe this is due to preventing default on the backspace event, and manually deleting characters instead.

It may be possible to accommodate this feature using some kind of timer that matches iOS behavior. If anyone would like to give that a try, you're welcome to. :)

[potlee]

I tired to fix this with #454. There seem be a constant number of single character deletions (22) before word deletions kick in, so that is what I used.