README.md: add zeroize

Author: tarcieri

README.md

@@ -14,6 +14,7 @@ This repository contains various utility crates used in the RustCrypto project.
 | `dbl` | [![crates.io](https://img.shields.io/crates/v/dbl.svg)](https://crates.io/crates/dbl) | [![Documentation](https://docs.rs/dbl/badge.svg)](https://docs.rs/dbl) | Double operation in Galois Field (GF) |
 | `hex-literal` | [![crates.io](https://img.shields.io/crates/v/hex-literal.svg)](https://crates.io/crates/hex-literal) | [![Documentation](https://docs.rs/hex-literal/badge.svg)](https://docs.rs/hex-literal) | Procedural macro for converting hexadecimal string to byte array at compile time |
 | `opaque-debug` | [![crates.io](https://img.shields.io/crates/v/opaque-debug.svg)](https://crates.io/crates/opaque-debug) | [![Documentation](https://docs.rs/opaque-debug/badge.svg)](https://docs.rs/opaque-debug) | Macro for opaque `Debug` trait implementation |
+| `zeroize` | [![crates.io](https://img.shields.io/crates/v/zeroize.svg)](https://crates.io/crates/zeroize) | [![Documentation](https://docs.rs/zeroize/badge.svg)](https://docs.rs/zeroize) | Securely zero memory while avoiding compiler optimizations |
 
 ## License