Update OpenCode editor (and potentially drop forked adjustments?)

OpenCode's editor should be updated, or maybe just dropped in favor of the upstream one maintained by the Italian DTD. There's no need to fork it just for the custom theme (they might have added different features though, I don't actually know if that's the case)

from https://github.com/publiccodeyml/publiccode.yml/issues/276#issuecomment-3834762189

I could not find a repository apart from this general one that would fit, feel free to move it to the correct repository/project.

I am not sure whether you even use a custom fork or so, but it seems https://editor.opencode.de/ at least the theme is indeed adjusted.

I could not find fork's source code as said, though.