Add API functionality

[Vipitis]

Part of #8

Adds functionality to directly interact with the shadertoy website via the api they offer (avoids copy and paste).
Also includes a basic CLI with entry point to test this easier. (requires force-reinstall via pip to show up)

> wgpu-shadertoy XcS3zK

Had snippets like this laying around from all the debugging anyway, it's really useful so polishing this up!
todos:

• add tests
• add dependencies numpy/Pillow
• [ ] consider locally caching shaders (at least media) -> maybelater PR
• setup an api key for github actions (?)
• add more examples
• update readme with CLI usage example
• clean up
• [ ] potentionally web scrape when shadertoy isn't officially available via the API? -> maybe there is a hash to predict this from the shaderID?