Add bytemuck support

[John Toohey]

I am using Uuids with bevy_ggrs_rollback, which requires bytemuck compatible types for serialization and deserialization. By adding the bytemuck feature, it would thus become possible to use Uuid with said library (and other similar libraries). Whilst it is possible to do this by using a newtype or the as_u128 and from_u128 methods directly, I believe that adding bytemuck support will make code using bytemuck cleaner.

Thank you for your time,

John T

[Ashley Mannix]

This is available as of 1.5.0