Create general unity article

[flibber-hk]

The article should essentially be an advert for the Scene.FindGameObject extension method, but cover how to use (typically in a subscriber to sceneLoaded or activeSceneChanged, when not to use (if the object has a component, you can get the object by hooking a method on the component) and why it might not work (if an object deparents itself you need to be able to match it before and after the deparenting).