Function onStart

onStart(cb: LifecycleMethod, opts?: LifecycleMethodOptions): () => void
Register a callback in the engine start event.
This happens once at the beginning of a frame
(e.g. once when the method is registered, after is created or the src has changed)
Parameters
- cb: LifecycleMethod
  The callback to be called. Optionally return a function that will be called when the onStart callback is removed again
- Optionalopts: LifecycleMethodOptions
Returns () => void
A function that can be called to unregister the callback
Example
```
onStart((ctx : Context) => {
    // do something
    console.log("Needle Engine: onStart registered")
    // optional to cleanup:
    return () => { console.log("OnStart removed") }
}
```