Add "Squoosh" web app

[Bustycat]

Squoosh, the well-known web app for image compression, has added the full support of QOI in October 2023. Users on Squoosh can import and preview a QOI image, and then convert it to another format such as WebP or JPEG XL; all image formats supported by Squoosh can be converted to QOI as well.

It is by far the most convenient tool for handling QOI.