message: feat(schema-bind): add map type to readme
diff: @@ -26,6 +26,7 @@ MessagePack encoded data is sent between module boundaries. Decoding of the mess
  | BigInt | fixstr or str 8/16/32 | UTF-8 string. |
  | JSON | fixstr or str 8/16/32 | UTF-8 string. |
  | [Type] | fixarray or array 16/32 | Array of elements. |
  +| Map | Msgpack extention type | Map of key-value pairs. |
  | type CustomObject {<br/>&nbsp;&nbsp;prop: Type<br/>} | fixmap or map 16/32 | Structured object. |
  ## Usage
  