TODO

* long term feature: shared_ptr less locator and resource cache
* custom allocators and EnTT allocator-aware in general (long term feature, I don't actually need it at the moment) - see #22
* debugging tools (#60): the issue online already contains interesting tips on this, look at it
* work stealing job system (see #100) + mt scheduler based on const awareness for types
* meta: sort of meta view based on meta stuff to iterate entities, void * and meta info objects (remove runtime views, welcome reflection)
* allow to replace std:: with custom implementations
* add examples (and credits) from @alanjfs :)
* static reflection, hint: template<> meta_type_t<Type>: meta_descriptor<name, func..., props..., etc...> (see #342)
* update documentation for meta, it contains less than half of the actual feature

WIP:
* pagination doesn't work nicely across boundaries probably, give it a look. RO operations are fine, adding components maybe not.
* make it easier to hook into the type system and describe how to do that to eg auto-generate meta types on first use
* add observer functions aside observer class
* introduce the component iterators for non-contiguous collections of entities (multi component views, observers, user defined collections)
* snapshot: support for range-based archives
* update snapshot documentation to describe alternatives
* custom pools.
* the Perfect Model.
* page size 0 -> page less mode
* add ::reach and rev iterators to proxy objects for faster and unsafe iterations
* add example: 64 bit ids with 32 bits reserved for users' purposes
* composable views and "faster views", deprecate non-owning groups
* offset instead of pages in the sparse set? top level mask for sparse sets?