src/defaults.ts: add fedi.buzz to servers

[astro]

#FediBuzz tries hard to see a lot of the Fediverse. In preparation for #38c3, I added the API that is used by this project.

As storing Fediverse content is regarded critically (really), #FediBuzz will only start collecting posts for a queried hashtag for up to 24 hours. That means the initially returned results will be empty if that hashtag hasn't been queried recently.

[defnull]

That's great! Seems to work for hashtag searches, but not for trends/timelines yet (e.g. "Show all trending posts"). Either fedi.buzz needs to support those too, or return empty results on those APIs, or Fediwall needs to better handle (and remember) errors and skip those APIs for future requests, or (and that may actually make the most sense) I special-case fedi.buzz in the sources and skip that domain for all but hashtag searches.

I added fedi.buzz to the 38c3 json (hosted on defnull.de) anyway, because that config only does hashtag and direct account searches. I'll look into integrating fedibuzz into fediwall better as soon as I find some time :) I like the idea.

[astro]

I don't think I'll ever be able to deliver all trending posts with the current approach of only caching content on demand.

• Returning empty results on my side is a bit feels a bit pointless to me. Pointless APIs always carry some incentive to put in static dummy data. ;-)
• I don't like hard-coding domain names because I'm using Mastodon for the decentralization aspects.
• Remembering errors to back off seems to be the best option that is generic enough to make sense with all other error-returning sources.