More examples/documentation request

Nobody has claimed this yet.

Hey @LinusU! This package looks awesome, but beyond the simple examples it gets to be quite the exercise of seeing how you structured things. I'd love to use this package more but more advanced cases have me lost at present.

I've got a Swift class I'm defining that needs to event back to JS, through a `EventEmitter.emit(...)`. `EventEmitter`'s prototype is added to the NAPI class through `utils.inherit(...)` on the JS side before instantiation. I'm having a hard time seeing how this is possible without the object's receiver one would use with `napi_call_function`?

Here's the TypeScript...
```typescript

import * as utils from 'utils'
import { BindingClass } from ('.build/release/binding')

util.inherits(BindingClass, events.EventEmitter)

export { BindingClass }
```

You see, I need to access the `emit` function added to the `BindingClass` prototype.

```swift
class BindingClass: NSObject {
init(_ env: OpaquePointer) { ... }

func fireEvent(name: String) {
let emit = /* ... get JS emit function from self */

// Emit event
emit.call(env, name)
}
}
```

Any chance of more docs or examples with classes?

Start with the package's existing simple examples and the TypeScript usage shown in the issue, especially utils.inherit, EventEmitter.emit, and napi_call_function. Trace how BindingClass and its Swift fireEvent method could be explained for a class that emits events to JavaScript. Done means adding an advanced class example or documentation that covers this EventEmitter use case.

Written by the indexing model from the issue text.