Updated v_2_0_cpp_x3_parse (markdown)

v_2_0_cpp_x3_parse.md

@@ -21,11 +21,18 @@ Define `MSGPACK_USE_X3_PARSE` before including `msgpack.hpp`. It is usually defi
 
 ## APIs
 
+### parse
 ```cpp
 template <typename Iterator, typename Visitor>
 inline bool parse(Iterator&& begin, Iterator&& end, Visitor&& vis);
 ```
 
+`Visitor` need to satisfy [visitor concept](https://github.com/msgpack/msgpack-c/wiki/v2_0_cpp_visitor).
+If `begin` is non-const lvalue, then it will be updated after successfully parsed.
+
+See an [example](https://github.com/redboltz/msgpack-c/blob/x3_parse/example/x3/parse.cpp).
+
+### unpack
 ```cpp
 template <typename Iterator>
 msgpack::object_handle unpack(
@@ -54,6 +61,12 @@ msgpack::object unpack(
     Iterator&& begin, Iterator&& end,
     unpack_reference_func f = MSGPACK_NULLPTR, void* user_data = MSGPACK_NULLPTR,
     unpack_limit const& limit = unpack_limit());
+```
+
+They are similar to https://github.com/msgpack/msgpack-c/wiki/v2_0_cpp_unpacker#client-controls-a-buffer. The APIs take a pair of iterators instead of data and len. 
+
+See an [example](https://github.com/redboltz/msgpack-c/blob/x3_parse/example/x3/unpack.cpp).
+
+## Stream parse/unpack
 
-https://github.com/redboltz/msgpack-c/blob/x3_parse/include/msgpack/v2/x3_parse.hpp#L846