Rename math/add.py to maths/add.py (#1857)

* Rename math/add.py to maths/add.py

* fixup! Format Python code with psf/black push

* Fix sum to add

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: John Law <johnlaw.po@gmail.com>

maths/add.py

@@ -0,0 +1,19 @@
+"""
+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 {add(a, b)}")