deny(missing_docs) at crate root

To help flag missing documentation on publicly accessible APIs.
diff --git a/src/rust_slice.rs b/src/rust_slice.rs
index b7b82e4..65fa87d 100644
--- a/src/rust_slice.rs
+++ b/src/rust_slice.rs
@@ -1,3 +1,5 @@
+#![allow(missing_docs)]
+
 use core::mem::{self, MaybeUninit};
 use core::ptr::{self, NonNull};
 use core::slice;