gh-106318: Add examples for str.ljust() method (#142719)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Doc/library/stdtypes.rst

@@ -2261,6 +2261,19 @@ expression support in the :mod:`re` module).
    done using the specified *fillchar* (default is an ASCII space). The
    original string is returned if *width* is less than or equal to ``len(s)``.
 
+   For example:
+
+   .. doctest::
+
+      >>> 'Python'.ljust(10)
+      'Python    '
+      >>> 'Python'.ljust(10, '.')
+      'Python....'
+      >>> 'Monty Python'.ljust(10, '.')
+      'Monty Python'
+
+   See also :meth:`rjust`.
+
 
 .. method:: str.lower()