Allow use of ArrayBuffer

[micahbf]

I am using jschardet in a browser context, where I have a file as an ArrayBuffer instead of the Node.js Buffer.

It could be nice to add the ArrayBuffer equivalent of this:

jschardet/src/index.js

Line 50 in a1c0607

u.feed(buffer.toString('binary'));

Which I believe to be this:

const binaryString = String.fromCharCode(...new Uint8Array(arrayBuffer));

If this sounds right, I could file a PR for this.