cJSON.h warn about write access to constants (#80)

Add a comment that warns about potential write access to constant memory
locations after using cJSON_AddItemToObjectCS.

cJSON.h

@@ -117,7 +117,10 @@ extern cJSON *cJSON_CreateStringArray(const char **strings, int count);
 /* Append item to the specified array/object. */
 extern void cJSON_AddItemToArray(cJSON *array, cJSON *item);
 extern void	cJSON_AddItemToObject(cJSON *object, const char *string, cJSON *item);
-extern void	cJSON_AddItemToObjectCS(cJSON *object, const char *string, cJSON *item);	/* Use this when string is definitely const (i.e. a literal, or as good as), and will definitely survive the cJSON object */
+/* Use this when string is definitely const (i.e. a literal, or as good as), and will definitely survive the cJSON object.
+ * WARNING: When this function was used, make sure to always check that (item->type & cJSON_StringIsConst) is zero before
+ * writing to `item->string` */
+extern void	cJSON_AddItemToObjectCS(cJSON *object, const char *string, cJSON *item);
 /* Append reference to item to the specified array/object. Use this when you want to add an existing cJSON to a new cJSON, but don't want to corrupt your existing cJSON. */
 extern void cJSON_AddItemReferenceToArray(cJSON *array, cJSON *item);
 extern void	cJSON_AddItemReferenceToObject(cJSON *object, const char *string, cJSON *item);