Ruby 3.3 WIP (trimmed)

Simplified a lot of the dockerfile.

Web server works locally, but not on GitHub codespace.

Rake tests run in both places.

Ruby 3.3 WIP

Upgrade to Ruby 3.3.

rack tests pass, but app won't launch yet.
First version with devcontainer.

Ruby 2.7

Old code that runs on Ruby 2.7.