Add a "Fediverse" URL for profiles

[jamietanna]

My website uses a Fediverse-compatible app, https://fed.brid.gy/ to bridge between my website and the Fediverse.

I noticed that my Mastodon link in my profile was resulting in a 404 link, as I had set @[email protected] (which is a valid Fediverse profile), which Changelog redirects to https://www.jvt.me/@www.jvt.me.

(I've since set up a redirect to correctly point folks from there to a separate page)

This would also be useful for folks on different Fediverse tooling, but do not conform to the username -> URL remapping that Mastodon does.

For instance @[email protected] remaps to (404ing) https://yeet.ols.wtf/ols whereas Ols' profile page is at https://yeet.ols.wtf/u/ols.

This would allow folks to use Mastodon @ profile-to-URL remapping, or choose to use a full URL if they wanted.