Autosize textarea width support

Hello.

I just thought that it could be neat to have `width` of `textarea` to be also autosizable.
[Proof of concept](https://github.com/kengho/react-textarea-autosize).

I used approach to search for the largest `width` that gives the lowest `textarea.scrollHeight` (since `textarea.scrollWidth` seems not to show correct value (maybe I'm wrong about that)).
```
width => textarea.scrollHeight
1 => 1000
2 => 500
3 => 200
4 => 80
5 => 80
6 => 70 <= answer
7 => 70
8 => 70
9 => 70
```
I couldn't figure out better way that using binary-ish search yet, but maybe there are better ways (I'm sure about that; for example, it could be possible to apply default JS sort using some kind of array emulation, or maybe there are even cleanest ways), and also maybe there are devs that will use this feature even considering higher resources consumption.

Btw, in regular-sized textareas this approach gives acceptable result after 5-10 iterations.

What do you think?