Smarter Social Metadata

[skial]

Currently the social metadata uses the same image, post type, author info etc for every article.

• [ ] This isn't a problem if haxe.io continues to just be me creating posts, but I want contributor and author information to be correct.
• [x] A picture in the post should be used instead of my logo, which should also change the twitter card type.
• [ ] If a video is in the post and marked to be used as the social card, adapt.