Align rendering of the feed across kinds

To make it a bit nicer between articles and /mf2/ entries, we should move to using a more consistent feel between kinds.

Firstly this requires making the presentation of the articles smaller, and a bit less bold in the feed, while taking care to preserve the Microformats2 content of the post.

Articles' titles should be a bit bolder than regular text, but not as big as an h1 previously.

Following influence from https://mrkapowski.com/ we can decorate the post with details of the kind of post it is. To make it more extensible, we can create a new kinds data setup, which can contain information about each of the kinds, such as the icon.