Potential improvements

[randy408]

• make deserialize_type() non-recursive(?) and use depth variable to make error messages more descriptive, e.g. foo.bar.array[2]: invalid type

• Expose JSON module?

• System status callback?

• Consider v2.4-style API for systems, entities, etc

• Move from fragile macros to using the internal import_handles() function for exposing builtin flecs entities/components