Bevy Ptr

The bevy_ptr crate provides low-level abstractions for working with pointers in a more safe way than using rust's raw pointers.

Rust has lifetimed and typed references (&'a T), unlifetimed and typed references (*const T), but no lifetimed but untyped references. bevy_ptr adds them, called Ptr<'a>, PtrMut<'a> and OwningPtr<'a>. These types are lifetime-checked so can never lead to problems like use-after-frees and must always point to valid data.