Add simple is_even algorithm

Author: BhumikaB1

maths/is_even.py

@@ -0,0 +1,8 @@
+def is_even(n: int) -> bool:
+    """
+    Check whether a number is even.
+
+    :param n: Integer number
+    :return: True if even, False otherwise
+    """
+    return n % 2 == 0