It's intended to be simple though we can definitely use some better documentation in this area. All you need to do is pass in a config. You can take a look at some configs in src/format.coffee. Most are just a few lines (though we need to document what they mean). For example link is just { tag: 'A', attribute: 'href' }.

Realistically though will probably end up adding all of the common formats leaving just custom ones for the user. But even custom ones should be simple. For example all we did to define a custom authors format in the Authorship module was quill.addFormat('editor', { class: 'author-' }).

Better documentation (and more predefined formats) to come!