Support for importing/exporting images in Qoi format

[Lehonti]

This format has gained a lot of traction in several fields despite being relatively new (just a few years old) because

• It is simple (the entire spec fits in one page)
• The spec is under the public domain
• It has been designed to be fast to encode and decode
• It is said to achieve a similar level of compression to PNG
• It is lossless
• It is supported by several popular tools like FFmpeg and GIMP
  https://en.wikipedia.org/wiki/QOI_(image_format)
  https://qoiformat.org/

Update: I am not familiar with the architecture gdk-pixbuf, but it seems that it might already support Qoi. If it does, how long might it take until the functionality reaches Pinta? https://github.com/GNOME/gdk-pixbuf/blob/master/gdk-pixbuf/io-glycin-qoi.c

[cameronwhite]

If there's a glycin pixbuf loader then it might already be working on the flatpak package (or any environment with a new enough gdk-pixbuf, e.g. GNOME 49+). AFAIK gdk-pixbuf only supports the glycin loaders on Linux though