add QOI Image format

[lastrosade]

My first PR on this project!

Adds support for the QOI image format.
Adds qoi.h as a new dependency in thirdparty/.

QOI is a fast image format, according to its creator: It losslessly compresses images to a similar size of PNG, while offering 20x-50x faster encoding and 3x-4x faster decoding.
Some of us may be interested in using QOI in our pipelines/workflows. (I do and Green-Sky had expressed interest in it)

I do not write a lot of C++ so I hope this is good.

This should cover both the cli and server frontends. I have tested the cli with both input and output, I have barely tested the server, I would do more if I knew what the API is and how to interact with it :)
Note that the produced QOI files will not contain any metadata such as inference parameters, models, etc...

[Green-Sky]

QOI all the tings!

I would like to see metadata though. The most "offical" way is to append json to the file.

edit: Another thing to add, beside the encoding/decoding speedup, is the size reduction compared to stbi png. qoi should be about x0.75-x0.90 the size of stbi pngs, so always smaller.

[lastrosade]

I would also like to see metadata in QOI, a simple kv list or even straight up CBOR. But breaking compatibility won't help us lol.

[Green-Sky]

I would also like to see metadata in QOI, a simple kv list or even straight up CBOR. But breaking compatibility won't help us lol.

You meant msgpack right? :)

Jokes aside, appending json wont break compatibility. Any (compliant) qoi parser will ignore anything that is appended after the image to the file.
see phoboslab/qoi#294 (comment)