Javadoc
Checks if the chunk belongs to this relevance region and adds it to it if it is relevant.
This method does explictly not care for the readyness of the chunk (light calcualted) or not: The light
calculation gets only performed once the adjacent chunks got loaded. So if wait for the light calculation
before we mark a chunk as relevant for a client then we would transfer less chunks to the client then the
relevance region is large. the client would then again perform the light calculation too based on that
reduced chunk count and would reduce the view distance again. That is why it makes sense to detect
chunks as relevant even when no light calculation has been performed yet.