Move demo code to package, add makefile

Makefile

@@ -0,0 +1,6 @@
+
+.ONESHELL:
+serve:
+	poetry run  uvicorn papi.main:app
+
+

papi/main.py

@@ -0,0 +1,15 @@
+from typing import Optional
+
+from fastapi import FastAPI
+
+app = FastAPI()
+
+
+@app.get("/")
+def read_root():
+    return {"Hello": "World"}
+
+
+@app.get("/items/{item_id}")
+def read_item(item_id: int, q: Optional[str] = None):
+    return {"item_id": item_id, "q": q}