compatibility with latest Sketch 49 Javascript API
Maybe I am doing something wrong but I expected that this would work:

`
export default function(context) {
  var sketch = require('sketch')
  context.document.showMessage("It's alive 🙌")
}
`

Base on http://developer.sketchapp.com/reference/api/#installation 

It throws the following error:
Module not found: Error: Can't resolve 'sketch' in ' /path/to/plugin/my-comman.js

And in the code, it shows this:
`
 var sketch = __webpack_require__(!(function webpackMissingModule() { var e = new Error("Cannot find module \"sketch\""); e.code = 'MODULE_NOT_FOUND'; throw e; }()));
`
I guess that normally you would want to install it as a module but this is kind of an exception according to sketch. 

The API comes bundled inside Sketch, so no installation is required. You access it by calling the global require function.

