[Marouane-elfadli]

Adds .bik (Bink Video) as a read-only video format: FFmpeg's bink demuxer and decoder read it, so it converts to every video and audio target. Existing libraries learn it on the video donut (settings step v56).

Fixes #751

(.lst was taken out of this PR: #767 asks for .lst → MP4, which needs to know what the file holds first.)

[KnifeLemon]

Thanks, @Marouane-elfadli! .bik is a good addition: FFmpeg reads every video format in the registry, so registering it is all it takes.

I pushed one commit (960e645) to finish it, and changed the title and description to match:

• .lst is out of this PR. [Format]: .lst #767 asks for .lst → MP4, and as a text format it could only become TXT or PDF, so "Fixes [Format]: .lst #767" would have closed the request without doing it. A .lst that should become a video is most likely a list of video pieces (like .m3u8 in Format request: .m3u8 #689), so I asked the reporter there what the file holds.
• README count 269 → 270 in all 15 READMEs (.bik is a new format).
• docs/ENGINES.md: a short Bink paragraph next to .dav.

I'll merge once CI passes.

[KnifeLemon]

CI passes with the follow-up commit. Thanks again, @Marouane-elfadli!