[jerryx/arg]add jerryx_arg_utf8_string (#2133)

JerryScript-DCO-1.0-Signed-off-by: Zidong Jiang zidong.jiang@intel.com

docs/09.EXT-REFERENCE-ARG.md

@@ -28,6 +28,7 @@ typedef struct
 - [jerryx_arg_number](#jerryx_arg_number)
 - [jerryx_arg_boolean](#jerryx_arg_boolean)
 - [jerryx_arg_string](#jerryx_arg_string)
+- [jerryx_arg_utf8_string](#jerryx_arg_utf8_string)
 - [jerryx_arg_function](#jerryx_arg_function)
 - [jerryx_arg_native_pointer](#jerryx_arg_native_pointer)
 - [jerryx_arg_ignore](#jerryx_arg_ignore)
@@ -461,7 +462,7 @@ jerryx_arg_boolean (bool *dest,
 **Summary**
 
 Create a validation/transformation step (`jerryx_arg_t`) that expects to
-consume one `string` JS argument and stores it into a C `char` array.
+consume one `string` JS argument and stores it into a CESU-8 C `char` array.
 
 **Prototype**
 
@@ -482,6 +483,36 @@ jerryx_arg_string (char *dest,
 **See also**
 
 - [jerryx_arg_transform_this_and_args](#jerryx_arg_transform_this_and_args)
+- [jerry_arg_utf8_string](#jerry_arg_utf8_string)
+
+
+## jerryx_arg_utf8_string
+
+**Summary**
+
+Create a validation/transformation step (`jerryx_arg_t`) that expects to
+consume one `string` JS argument and stores it into a UTF-8 C `char` array.
+
+**Prototype**
+
+```c
+static inline jerryx_arg_t
+jerryx_arg_utf8_string (char *dest,
+                        uint32_t size,
+                        jerryx_arg_coerce_t coerce_flag,
+                        jerryx_arg_optional_t opt_flag)
+```
+
+ - return value - the created `jerryx_arg_t` instance.
+ - `dest` - pointer to the native char array where the result should be stored.
+ - `size` - the size of native char array.
+ - `coerce_flag` - whether type coercion is allowed.
+ - `opt_flag` - whether the argument is optional.
+
+**See also**
+
+- [jerryx_arg_transform_this_and_args](#jerryx_arg_transform_this_and_args)
+- [jerry_arg_string](#jerry_arg_string)
 
 
 ## jerryx_arg_function