[Feat Req] A way to set a certain Attr of a Tag regardless of whether its specified

[davidfurlong]

I want to make sure that a tags have a rel='nofollow' attr. Perhaps this is beyond the scope of this library. However onTagAttr and safeAttrValue seem to only work in terms of removing specified attrs. If this attr isn't specified, it won't get fired. Thx & feel free to close if you want

[Kolobok12309]

@davidfurlong, you can do something like this if with rel, for remove rel attr before href(browser will ignore second attr with the same name)

onTagAttr(tag, name, value, isWhiteAttr) {
      if (!isWhiteAttr) return;
      if (tag === 'a') {
        if (name === 'rel') return '';
        if (name === 'href') {
          return `href="${xss.escapeAttrValue(value)}" rel="nofollow"`;
        }
      }
    },