Currently, pressing [tab] makes the editor lose its focus. Does prosemirror support tabstops? If not, then what is the best/easiest approach to fake them? I suppose, on pressing tab, the editor could insert a “wide-space” element (a div that is about 4em wide). This is not the same as tab, I know, but at least it produces something which is reasonably useful (tabs are often used at the beginning of a paragraph anyway).