Update to v6.21.5

extras/tests/Misc/issue1967.cpp

@@ -0,0 +1,13 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2023, Benoit BLANCHON
+// MIT License
+
+// we expect ArduinoJson.h to include <string>
+#define ARDUINOJSON_ENABLE_STD_STRING 1
+
+// but we don't want it to included accidentally
+#undef ARDUINO
+#define ARDUINOJSON_ENABLE_STD_STREAM 0
+#define ARDUINOJSON_ENABLE_STRING_VIEW 0
+
+#include <ArduinoJson.h>