Module declaration wildcards

While stubbing out most modules is easy to do by just doing:

```
declare module 'module-name' {
declare module.exports: any;
}
```

Some modules provide _many_ files to import. For example, I use [react-icons](https://github.com/gorangajic/react-icons) which has hundreds of files. It would be nice if a module declaration would work like:

```
declare module 'react-icons/lib/*' {
declare module.exports: any;
}
```

and catch all of the modules under that path.