📝 Add docs for creating a custom Response class (#5331)

docs_src/custom_response/tutorial009c.py

@@ -0,0 +1,19 @@
+from typing import Any
+
+import orjson
+from fastapi import FastAPI, Response
+
+app = FastAPI()
+
+
+class CustomORJSONResponse(Response):
+    media_type = "application/json"
+
+    def render(self, content: Any) -> bytes:
+        assert orjson is not None, "orjson must be installed"
+        return orjson.dumps(content, option=orjson.OPT_INDENT_2)
+
+
+@app.get("/", response_class=CustomORJSONResponse)
+async def main():
+    return {"message": "Hello World"}