Add multiply helper to exercise CI and the review gate

app.py

@@ -18,3 +18,8 @@ def add(a: int, b: int) -> int:
 
 if __name__ == "__main__":
     print(greet("review-policy"))
+
+
+def multiply(a: int, b: int) -> int:
+    """Return the product of two integers."""
+    return a * b