📝 Update docs, add first tutorials

docs/tutorial/src/all/tutorial012.py

@@ -0,0 +1,13 @@
+from fastapi import FastAPI, Path
+
+app = FastAPI()
+
+
+@app.get("/items/{item_id}")
+async def read_items(
+    *, item_id: int = Path(..., title="The ID of the item to get"), q: str
+):
+    results = {"item_id": item_id}
+    if q:
+        results.update({"q": q})
+    return results