docs: improve description on how int is also a float

Author: bobleesj

src/diffpy/utils/validators.py

@@ -1,5 +1,8 @@
 def is_number(string):
     """Check if the provided string can be converted to a float.
+    
+    Since integers can be converted to floats, this function will return True for integers as well.
+    Hence, we can use this function to check if a string is a number.
 
     Parameters
     ----------