Misc. documentation issues / suggestions

[TedTed]

Going through the "From the web" section of the docs and finding a couple of issues / potential improvements:

• The "Bluesky" part of the custom domain section links to an issue that was downscoped to only cover Mastodon → Bluesky. It's unclear whether the same option is possible if the source of truth is a website instead of a Mastodon account.
• The example for including an image would benefit from including an alt-text.
• The section on post deletion seems to be in the wrong section of the table of contents of the page. Same for the brid.gy subdomains.
• It would be really nice to list a few examples of open-source software that are known to "play nice" with Bridgy Fed, e.g. send the right webmentions and messages that correspond to the expected microblogging format and so on.
• In the background section, do you want to mention anew.social?

[snarfed]

These are all great notes, thank you!