Add files directive to package.json to speed up installs
Add files directive to package.json to speed up installs

Used negate expressions in `package.json` files entry, although it goes
against recommendation below, because that's the only thing that
worked. Read the github references below for details.

> "The consequences are undefined" if you try to negate any of the files
> entries (that is, "!foo.js"). Please don't. Use .npmignore.

https://github.com/npm/npm/wiki/Files-and-Ignores#details

```text
.
├── LICENSE
├── README.md
├── docs
│   └── index.md
├── lib
│   ├── expect.js
│   └── referee.js
└── package.json
```

busterjs/referee