Add typed arrays

[domenic]

They're a somewhat major new ES6 feature, despite being in browsers already.

[lukehoban]

Good point, I've got some content I should be able to add.

[allenwb]

and mention that they sukpport most of the Array.prototype methods

[dead-claudia]

@ALL BTW I think it would be quicker to just send a PR at this point, given it's partially outdated ATM (Symbol.create no longer exists, Symbol.toStringTag has no coverage AFAICT, and the module loader was deferred into another spec).