I’m making a plugin that incidentally interacts with https://meta.discourse.org/t/topic-list-previews/41630.
My end goal is to display these http://bl.ocks.org/ in a post (which I have working), but I also want to display the thumbnail in the topic-item. I overrode ExcerptParser.rb methods to allow my custom tag to go through (akin to the spoiler class attribute on div and span). My hope is to grab the data within the allowed span tag and render the thumbnail after it uses this data to make an ajax request.