Add an example for str.capitalize for #106318

This is the smallest possible step toward adding examples for the string methods.
The content was  contributed by @adorilson in #105670
Because  #119445 is big and difficult to review,
this PR will be updated as the individual examples get merged.

Author: blaisep

Doc/library/stdtypes.rst

@@ -1759,7 +1759,14 @@ expression support in the :mod:`re` module).
 .. method:: str.capitalize()
 
    Return a copy of the string with its first character capitalized and the
-   rest lowercased.
+   rest lowercased. For example::
+
+      >>> 'PYTHON IS AMAZING'.capitalize()
+      'Python is amazing'
+      >>> 'Njemačka Starts With a non-english Digraph'.capitalize()
+      'Njemačka starts with a non-english digraph'
+
+   See also :meth:`title`.
 
    .. versionchanged:: 3.8
       The first character is now put into titlecase rather than uppercase.