Use Flickr's slideshow embed for album links

[elfprince13]

Is your feature request related to a problem? Please describe.

Flickr is a photography sharing site. When I post a link to a Flickr album on Mastodon, it uses the Flickr embedded slideshow player; however, when I post a link to a Flickr album on Bluesky it just shows a link to an external page with the album preview. Anecdotally, users seem much more willing to press "play" on an embedded link than to click a link that will open an external web page.

Describe the solution you'd like

Recognize links of the form https://www.flickr.com/photos/elfprince13/albums/NNNNN and generate an embedded player using a rewritten link of the form https://embedr.flickr.com/photosets/NNNNN

Working example NNNNN=72177720316092109

Additional context

I believe this should be a fairly mechanical set of changes to the files modified by #2353, but wanted to get feedback before submitting a PR.