Kap: Split the `ffmpeg` download script into a separate package

[albinekb]

Hi! Kap's convert functions is very useful for other things than kap, what do you think of making them their own lib?

Also, it would be 👌 to do the same with ffmpeg?

I'll help if you agree 🎉

🙏

[sindresorhus]

I agree about splitting out the ffmpeg download thing or use something that exists, but not sure about convert.js. It's nice having it in the repo for now so we can iterate quickly on it. Can always be extracted later on. If we extract convert.js, other projects will start using it and come with demands that we don't need and it's going to be hard to keep it focused.

[sindresorhus]

Ugh, it's really annoying that the ffmpeg script runs every time I run npm install. We should prioritize getting it into a separate package.

[sindresorhus]

Existing modules:

• https://www.npmjs.com/package/ffmpeg-static (all OSes)
• https://www.npmjs.com/package/ffbinaries (all OSes)
• https://www.npmjs.com/package/ffmpeg-downloader (downloads only the current platform binary)
• https://www.npmjs.com/package/@ffmpeg-installer/ffmpeg (downloads only the current platform binary)

The last one looks like our best option.