Statically grab and include webmentions during Hugo builds, no JS
involved. Hugo supports making web requests and parsing the resulting
JSON, so there was no need to use an external program either.
Inspired by the h-entry implementation on Charlie Owen's personal
website: https://whalecoiner.com
The u-photo re-uses the 32px favicon that the browser has already
cached, so it shouldn't bloat up the page anymore.
These changes required a bit of additional CSS. I snuck in come color
changes too.
