Add autopair functionality

[davidsanchez222]

For a lot of people coding in modern ides or that have a autopair plugin paired with tabout, typing closing parentheses are impractical. There should be a setting that enables them when you type so you only type the opening character and then press tab to exit out of it. So anytime these characters are typed: '"({[, they get closed with '")}] If this is something that you think is useful, I can work on a pull request for it.

P.S. I really love the website. It's awesome and I'll be using it everyday as opposed to monkeytype because it gives more useful practice than just the 125 most popular words.