[Feature Request] Get all users who can be impersonated?

Hi, I was looking for something or some way to get a list of all users who CAN be impersonated, is that something you'd consider adding to this library?

I can obviously do this on my own end, I just didn't know if this would represent a common enough use case to justify it being part of your solution.

I can always do something like this, not sure if there's a cleaner way here:

```
public static function impersonatable(){
return User::cursor()->filter(function ($user){
return $user->canBeImpersonated();
});
}
```

Your library is great though, thanks so much!