Rewrite posting process with card system and more structured API - The basic posting process is more opinionated so that silos have less code to write, and dry-run posting is handled by default. - Add "card" system where SiloRider is able to fetch the page of a post to check for any custom summary or featured image. This is how Twitter, Facebook, Discord, and many others come up with their "preview card" when a link is posted.