should be it

external/duckdb/extension/json/include/json_extension.hpp

@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//                         DuckDB
+//
+// json_extension.hpp
+//
+//
+//===----------------------------------------------------------------------===//
+
+#pragma once
+
+#include "duckdb.hpp"
+
+namespace duckdb {
+
+class JsonExtension : public Extension {
+public:
+	void Load(ExtensionLoader &db) override;
+	std::string Name() override;
+	std::string Version() const override;
+};
+
+} // namespace duckdb