Behaviour for mapping Quillon tokens onto CSS classes.

Quillon.HTML calls class/2 once per node and once per layout or styling token on that node, then joins whatever comes back into a single class attribute. Returning nil contributes nothing.

defmodule MyApp.DocClasses do
  @behaviour Quillon.HTML.Classes

  @impl true
  def class(:node, :blockquote), do: "doc-quote"
  def class(:align, :center), do: "u-center"
  def class(_property, _value), do: nil
end

Quillon.HTML.to_html(doc, classes: MyApp.DocClasses)

The property is :node for the node type itself, :mark for a mark type, and otherwise the attribute name - :align, :spacing, :color and the rest of the token vocabulary in Quillon.Types. A mapper is called for custom node and mark types too, so define a catch-all clause.

See Quillon.HTML.Tailwind for a complete implementation.