Update the Makefile to download the old version of the site, run
static-webmentions, and collect the WebMentions to send in a json file
saved as a build artifact.
Don't send these automatically; just save them for now. Until I work out
a solution to save sent WebMentions and avoid sending duplicates, I'll
keep the sending of WebMentions manual.
For some reason this caused webhint's axe/aria test to error out with a
"Protocol error" so I disabled it. Axe tests are covered by Lighthouse
anyway.
Compress with brotli ahead of time in CI, just like we do with zopfli
for gzip_static
Update hintrc to check for brotli compression.
Update lighthouse config to throttle CPU some more since brotli
decompression can be heavier.
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.
