code: function(inlines) {
    var m;
    if ((m = this.match(/^&(?:#x[a-f0-9]{1,8}|#[0-9]{1,8}|[a-z][a-z0-9]{1,31});/i))) {
        inlines.push({ t: 'Entity', c: m });
        return m.length;
    } else {
        return  0;
    }
  }
docs: Attempt to parse an entity, adding to inlines if successful.