Fetch support for Mastodon

[Fauli1221]

Is your feature request related to a problem? Please describe.
When I type in a link to a mastodon post with an art I want to upload it throws "No image found at that address."

The post I used is this https://equestria.social/@belkasempai/112690763717126019

Describe the solution you'd like
Fetch support for posts on Mastodon and other Fediverse software implementing the Mastodon api

[liamwhite]

The first step in fetching images from ActivityPub instances for art is determining whether the given domain supports being scraped as if it were Mastodon, which has to be done on a per-domain basis.

Mastodon, Pleroma, Akkoma, and Sharkey all have the same statuses API format. Misskey doesn't have that API.

AP instances also have the ability to fetch statuses from other instances which makes things a bit more complicated
because you need to resolve what the "home" instance is to properly fetch a status.