add a fact function to show that apidoc auto updates

src/fancymath/math.py

@@ -1,2 +1,15 @@
+"""
+This is some really Fancy Math!
+"""
+
 def add(x1, x2):
+    "Apply the + operator to two Python objects"
     return x1 + x2
+
+
+def fact(n: int) -> int:
+    "Return the factorial of n."
+    if n == 1:
+        return 1
+    else:
+        return n * fact(n - 1)