how to port codemirror 5 themes to codemirror 6

I have read the migration guide, but still can’t figure out how to do it.

For example port all the themes from CodeMirror: Theme Demo.

What’s steps should I follow to transform the css file to codemirror theme extension.

It will be so convenient to write a codemode using recase or jscodemode to automaticly transform all the v5 themes

thank you