gh-106318: Add link to Kharosthi numbers on Wikipedia (str.isdigit() method docs)

Author: adorilson

Doc/library/stdtypes.rst

@@ -2261,7 +2261,8 @@ expression support in the :mod:`re` module).
    character, ``False`` otherwise.  Digits include decimal characters and digits that need
    special handling, such as the compatibility superscript digits.
    This covers digits which cannot be used to form numbers in base 10,
-   like the Kharosthi numbers.  Formally, a digit is a character that has the
+   like the `Kharosthi numbers <https://en.wikipedia.org/wiki/Kharosthi#Numerals>`__.
+   Formally, a digit is a character that has the
    property value Numeric_Type=Digit or Numeric_Type=Decimal.
 
    For example: