[vx] add one stop install pkg @vx/vx

[hshoff]

Fixes #33. Thanks to @andyfangdz for the suggestion.

If you're not worried about bundle size or you just want to play around with vx packages without having to install each one you can now do:

npm install --save @vx/vx react react-dom

and then use it like so

import { scaleLinear, AreaClosed, withTooltip } from '@vx/vx';
console.log(scaleBand);
console.log(AreaClosed);
console.log(withTooltip);

// or put everything under a vx namespace
import * as vx from '@vx/vx';
console.log(vx.scaleBand);
console.log(vx.AreaClosed);
console.log(vx.withTooltip);

[williaster]

this is great! 🎉