Oh yeah I think schemas for helm charts are another example.

values.schema.json

Why it’s not a yaml I’m not sure.

Are there any examples of multiple file extensions outside of compression and archiving?

Ha, touché

I’m sure many royals from history are bigger financial losers in real terms

Is there a link to the tweet or did I miss it? I think you should link the tweet because screenshots are so easy to fake and (in other situations) to give credit