[3.13] gh-106318: Add examples for `str.startswith()` method (GH-144369) (#144480)

gh-106318: Add examples for `str.startswith()` method (GH-144369)
(cherry picked from commit 1b6d737ee0205521333cf5fe6ca6df2d3a6d4ec2)

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