Publish theme json schema v0.2.0 (#21428)

Fix theme json schema so `./script/import-themes print-schema` works again
Update schema to reflect current structs
([diff](https://gist.github.com/notpeter/26e6d0939985f542e8492458442ac62a/revisions?diff=unified&w=))

https://zed.dev/schema/themes/v0.2.0.json