message: Move docs comment to package module level
diff: +//! The crypto crate is intended to be used in internal crates / utils.
  +//! Please don't use any of these types directly, as
  +//! they might change frequently, or be removed in the future.
  +//! This crate does not adhere to semantic versioning.
  #![cfg_attr(feature = "backtraces", feature(backtrace))]
  mod crypto;
  mod errors;
  mod identity_digest;
  -/// The crypto crate is intended to be used in internal crates / utils.
  -/// Please don't use any of these types directly, as
  -/// they might change frequently, or be removed in the future.
  #[doc(hidden)]
  pub use crate::crypto::secp256k1_verify;
  #[doc(hidden)]
  