message: Add HexBinary to docs
diff: @@ -28,6 +28,7 @@ types as well as cosmwasm_std types and how they are encoded in JSON.
  | [Decimal] | string containing decimal number | `"55.6584"` | |
  | [Decimal256] | string containing decimal number | `"55.6584"` | |
  | [Binary] | string containing base64 data | `"MTIzCg=="` | |
  +| [HexBinary] | string containing hex data | `"b5d7d24e428c"` | |
  [uint64]: https://docs.rs/cosmwasm-std/1.1.1/cosmwasm_std/struct.Uint64.html
  [uint128]: https://docs.rs/cosmwasm-std/1.1.1/cosmwasm_std/struct.Uint128.html
  @@ -37,5 +38,7 @@ types as well as cosmwasm_std types and how they are encoded in JSON.
  [decimal256]:
  https://docs.rs/cosmwasm-std/1.1.1/cosmwasm_std/struct.Decimal256.html
  [binary]: https://docs.rs/cosmwasm-std/1.1.1/cosmwasm_std/struct.Binary.html
  +[hexbinary]:
  + https://docs.rs/cosmwasm-std/1.1.1/cosmwasm_std/struct.HexBinary.html
  [^1]: https://www.json.org/
  