Add missing Doxygen documentation for NovelRT::ResourceManagement.

[RubyNova]

As per the title, a new namespace has been introduced into the main branch. This namespace is lacking documentation, however.

It should be fairly straightforward to do - it should be a case of going through all the headers that were added as a part of that (not including TemporaryFnPtrs.h as its...well...temporary) and adding the correct doxygen documentation, similar to how its been handled in other places such as NovelRT::Ecs.