message: adjust documentation of chain-addr
diff: //! Account key:
  //! DISCRIMINATION_BIT || ACCOUNT_KIND_TYPE (7 bits) || STAKE_KEY
  //!
  +//! Multisig key:
  +//! DISCRIMINATION_BIT || MULTISIG_KING_TYPE (7 bits) || MULTISIG_MERKLE_ROOT_PUBLIC_KEY
  +//!
  //! Address human format is bech32 encoded
  //!
  