Feat: Multi scene injection support

[Ragueel]

Is your feature request related to a problem? Please describe.
When scenes are loaded additively, objects inside them are not getting their dependencies resolved.

Describe the solution you'd like
Maybe add a custom scene loading handler or custom scene manager.

Describe alternatives you've considered
Listen to scene load events and resolve dependencies. Alternatively, exposing SceneInjector might do the trick.

[gustavopsantos]

@Ragueel Does your additive scenes have any SceneContext? Even without any intaller.

[gustavopsantos]

@Ragueel I think maybe you forgot about adding a SceneContext to your scene.
If you read the documentation, SceneContext its not needed on all scenes, but, if you want Injection to happen once that scene is loaded, then you must have a SceneContext on it.
Not reproducible.