Add cross product impleimentation

src/fancymath/vector.py

@@ -36,6 +36,14 @@ class Vector(object):
         z = self.z + other.z
         return self.__class__(x, y, z)
 
+    def __mul__(self, other):
+        if not isinstance(other, Vector):
+            return NotImplemented
+        x = self.y * other.z - self.z * other.y
+        y = self.z * other.x - self.x * other.z
+        z = self.x * other.y - self.y * other.x
+        return self.__class__(x, y, z)
+
 
 if __name__ == "__main__":
     v1 = Vector(3, 4, 0)