added add algorithm (#1856)

* added add algorithm

* Update and rename check/add.py to math/add.py

Co-authored-by: Christian Clauss <cclauss@me.com>

math/add.py

@@ -0,0 +1,17 @@
+"""
+Just to check
+"""
+def add(a, b):
+    """
+    >>> add(2, 2)
+    4
+    >>> add(2, -2)
+    0
+    """
+    return a + b
+
+
+if __name__ == "__main__":
+    a = 5
+    b = 6
+    print(f"The sum of {a} + {b} is {sum(a, b)}")