entt/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
* 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
* custom pools example (multi instance, tables, enable/disable, and so on...)

WIP:
* HP: remove storage category and get_as_tuple, make storage classes return tuple (+ view generator detect shared storage in future)?
* HP: review registry::get, registry::try_get
* HP: weak reference wrapper example with custom storage.
* HP: merge view and view pack
* HP: invalid view auto-refresh
* HP: paginate pools
* HP: headless (sparse set only) view
* HP: write documentation for custom storages and views!!
* HP: registry: use a poly object for pools, no more pool_data type.
* HP: make runtime views use opaque storage and therefore return also elements.
* HP: add exclude-only views to combine with packs
* HP: entity-aware observer, add observer functions aside observer class
* HP: any and the like: remove constructor that accepts reference wrapper, allow only in-place T&?
* deprecate non-owning groups in favor of owning views and view packs, introduce lazy owning views
* pagination doesn't work nicely across boundaries probably, give it a look. RO operations are fine, adding components maybe not.
* snapshot: support for range-based archives
* page size 0 -> page less mode
* add example: 64 bit ids with 32 bits reserved for users' purposes
* add meta dynamic cast (search base for T in parent, we have the meta type already)