Version changer for Demo Site

Please include a library version changer in the demo site so users can browse outdated versions of the library. This is helpful particularly while working with generated AI code. There is no way for me to synthesize examples from the demo site into my understanding of the AI's code.

The issue names only the demo site and provides no files, tests, or entry points. First locate the demo site's version and build entry points, then determine how published library versions are made available; done means users can select and browse an outdated library version from the demo site.

Written by the indexing model from the issue text.