ruby: Use the Ruby image as the base

[stevehipwell]

The current Ruby example uses Alpine as the base instead of the official Wolfi based Ruby image; could this be updated?

I also have some questions about the example and melange in general, I'd be happy to open them as separate issues if that would be more appropriate?

• Why isn't the bundler install command frozen?
• Why is the lock file only configured for a single arch?
• How does melange make packages dependent on either musl (Wolfi) or glibc (Alpine)?
• Should there be a musl Ruby image?
• Is musl coming to Wolfi?