Add WebP output support

[CMiksche]

WebP offers the same quality and also animations, but needs way less data. (One GIF of mine was 171 KB and the same as WebP was just 13 KB)

[LarryBattle]

Output to a webm video format, then include it using the video HTML5 tag.

More info:

• https://github.com/charmbracelet/vhs#output
• https://en.wikipedia.org/wiki/WebP
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/video

[CMiksche]

Output to a webm video format, then include it using the video HTML5 tag.

WebM is a video format, I want an animated picture, which WebP also offers (see the "Animation" part in your linked Wikipedia article)

You can include WebP in your GitHub / GitLab Repos. I never saw someone using a video format inside a repo...

[maaslalani]

@CMiksche we'll definitely implement this feature! Will be cool to have webp animated images! Thank you for creating this issue!

[the8472]

For anything containing sharp, high-contrast edges (such as rendered fonts) you'll want a media format that supports 4:4:4 chroma.
At least the lossy version of webp uses 4:2:0 chroma subsampling. The lossless version could be used but it most likely doesn't compress as well.

The following web-compatible formats should support full chroma:

• apng
• webm with vp9 profile 1
• webm with av1 high profile
• mp4 with av1, h.264 or h.265 with the appropriate profile (usually called "High" or "Main 4:4:4")
• avif
• gif¹

¹ no chroma subsampling, but of course it still suffers from its limited palette