Describe the request

If someone uses Phosh to take a screenshot, it is copied to the clipboard vs. saved to disk: https://gitlab.gnome.org/World/Phosh/phosh/-/issues/964

We should probably be able to take a copied image and paste it to a new post.

Implementation Details

• This should be an option in settings.
• This should be only available to some fediverse backends. (Include which ones on the above field).
• This is client-only (and shouldn't sync with the instance).
• This follows the GNOME HIG.