Implementing annotations for ideographic languages with the HTML <ruby> tag

2

You can do something like this:

toDOM: () => [
        'ruby',
        { lang: 'jojo' },
        ['span', 0],
        ['rt', { rtlang: 'ji' }, '1'],
      ]

But as you can tell, Prosemirror follows the rule : Content hole must be the only child of its parent node, for which you will have to wrap the 0 in a span or something more appropriate.