Macro register_extensions 

macro_rules! register_extensions {
    ($world:expr, $($ty:ty => $name:expr),+ $(,)?) => { ... };
}

Register multiple extension types for snapshot deserialization in one call.

Eliminates the manual register_ext ceremony after snapshot restore.

Example

register_extensions!(sim.world_mut(), VipTag => "vip_tag", Priority => "priority");