Add rel attributes: "sponsored" and "ugc"

Nice, I just found the same and I think this important and super helpful for text filters, instead of the current "nofollow" checkbox!
Especially for comments (and the filtered_html / basic_html input filter) this makes a lot of sense.

Make sure that all external links that are tagged with the rel="nofollow" attribute really have to be tagged with this attribute. Google recommends using the rel="sponsored" attribute for sponsored links and the rel="ugc" attribute for user-generated content in links (e.g. comments). The rel="nofollow" attribute makes it clear to search engines that you do not want to link your page to the website to which you want to create a link.

So clear +1, not only for link.module but also and especially for text filters!

Thank you for your suggestion to improve Drupal Core! I'm going to close this as a duplicate of ✨ Add features of link attributes module to core's link module Active which is an issue to bring the link_attributes module into Core. It doesn't look like the link_attributes widget has an interface for selecting pre-defined rel values, but maybe that's something that could be added during the port to Core.