Update and fix some issues in EXT-REFERENCE documentation (#5180)

There was some issues and typos in the EXT-REFERENCE documentation.
This patch fixes these issues and typos.

JerryScript-DCO-1.0-Signed-off-by: Gergo Csizi gergocs@inf.u-szeged.hu

docs/10.EXT-REFERENCE-HANDLER.md

@@ -24,7 +24,7 @@ The engine must be initialized before specifying the `jerry_value_t` in the stru
 typedef struct {
   const char *name;
   jerry_value_t value;
-} jerryx_function_list_entry;
+} jerryx_property_entry;
 ```
 
 **See also**