Documenting our preview generation process

[nullishamy]

If not done already, it would be nice to document how exactly to generate previews.

This could provide links to docs on using an editor like GIMP to create each flavor, show how to use imagemagick (or similar) to convert those to webp (if needed), along with describing a simple catwalk command.

If this does exist, it would be good to put a link to it in the catwalk readme.

[uncenter]

We've been recommending the usage of cwebp for PNG -> WebP conversion over at the userstyles repository FYI: https://github.com/catppuccin/userstyles/blob/main/docs/tips-and-tricks.md#how-do-i-convert-preview-images-to-webp.

[nullishamy]

Any particular reason?

[uncenter]

Most accurate, as it is Google's official tool/library for it. I believe we found some issues with colors not being converted correctly/accurately with ImageMagick's convert command? It also is super simple to use.

[nullishamy]

Fair enough. I'm not biased in any particular way so that reason seems good as any. Would also mean that we are consistent org-wide, which is nice.

Just need to think about where this would go. After that I'd be willing to PR some docs in.