Update AddTwoNum.py

done some code because it was easy
if there is any error please update

Author: AkhileshThykkat

coding_solutions/interview_related/AddTwoNum.py

@@ -1 +1,8 @@
-'Solution to be add here'
+def add(x,y):
+  if x and y is not digit:
+    return None
+  else:
+    a,b = int(x), int(y)
+    return a + b
+    
+