deny(missing_docs) at crate root

To help flag missing documentation on publicly accessible APIs.
diff --git a/src/rust_vec.rs b/src/rust_vec.rs
index 8443043..e66519f 100644
--- a/src/rust_vec.rs
+++ b/src/rust_vec.rs
@@ -1,3 +1,5 @@
+#![allow(missing_docs)]
+
 use crate::rust_string::RustString;
 use alloc::string::String;
 use alloc::vec::Vec;