Update our kitchen sink

The kitchen sink reference is for demonstrating as much syntax and style for Sphinx builds as possible. It is copied directly from the sphinx-themes.org documentation so that we use standardized reference docs compared with other communities. The source files for these pages are stored in the sphinx-themes.org repository.

To update the kitchen sink source files, there is a helper Python script that will loop through the known kitchen sink files and copy over the latest text. To use it, run the following from the root of the repository: