EXAMPLES
* filter on runtime values/variables (not only types)
* support to polymorphic types (see #859)

DOC:
* custom storage/view
* update entity doc when the storage based model is in place
* in-place O(1) release/destroy for non-orphaned entities, out-of-sync model
* view: single vs multi type views are no longer a thing actually
* bump entities, reserved bits on identifiers

TODO:
* resource cache: avoid using shared ptr with loader and the others
* further optimize exclusion lists in multi type views (no existence check)
* further improve meta resolve function by id (bimap)
* get rid of observers, storage based views made them pointless - document alternatives
* deprecate non-owning groups in favor of owning views and view packs, introduce lazy owning views
* bring nested groups back in place (see bd34e7f)
* work stealing job system (see #100) + mt scheduler based on const awareness for types
* view: reduce inst due to/improve perf with index-based approach in dispatch_get/pick_and_each/each (single type too, define storage ::at and ::at_as_tuple)
* view: update natvis as needed after the last rework, merge pools/filter in the same array, drop check (?) and turn view into a position
* view: type-only view_iterator (dyn get/excl sizes), type-only basic_common_view (dyn get/excl sizes with pointer to array from derived)
* combine version-mask-vs-version-bits tricks with reserved bits to allow things like enabling/disabling
* maybe drop begin(v)/end(v) from sparse set and only use non-scoped begin/end at call sites
* review all // NOLINT + linter workflow + review clang-tidy file
* self contained entity traits to avoid explicit specializations (ie enum constants)
* auto type info data from types if present
* group review: use handler as base with protected members and arrays of common type (see view for further details)
* swap sets in swap-only mode, return scoped iterators by default, make ::free_list return an iterator if possible
* test: push sharing types further
* after non-continuous generation for entity storage:
  - get/reset placeholder to position after saving/loading (avoid long lookup)
  - documentation for reserved entities
* storage entity: no emplace/insert, rename and add a fast range-push from above
* view: review tombstone checks, no longer required with storage entity and Get 1
* natvis: entity viewer for the registry
* natvis: meta context?
* restore view simple in natvis for containers and the others, add more, they make sense! :)