Fix missing calls to on begin object/array

src/test.cpp

@@ -557,6 +557,7 @@ private:
     switch (*self->buf) {
     case '{':
       ++self->buf;
+      self->callbacks->on_begin_object(self->data);
       self->pop();
       if (Status s = self->push({N_OBJECT_VALUE_OR_END})) {
         return s;
@@ -564,6 +565,7 @@ private:
       break;
     case '[':
       ++self->buf;
+      self->callbacks->on_begin_array(self->data);
       self->pop();
       if (Status s = self->push({N_ARRAY_VALUE_OR_END})) {
         return s;