Add a tutorial "Exposing server options with profile_list" to docs

[consideRatio]

I think we should add a tutorial as defined in https://diataxis.fr/ to help users orient on how profile_list can be used and learn a bit with practical examples and images on how it can look.

Currently, KubeSpawner doesn't have anything besides reference docs generated from docstrings and a changelog. I think we should add a tutorials section, and add a tutorial to help users learn how to expose various server options using profile_list configuration.