Sync fastapi docs from 50fa3f7c on 2026-01-11

docs_src/custom_response/tutorial005_py39.py

@@ -0,0 +1,9 @@
+from fastapi import FastAPI
+from fastapi.responses import PlainTextResponse
+
+app = FastAPI()
+
+
+@app.get("/", response_class=PlainTextResponse)
+async def main():
+    return "Hello World"