[FEAT] Shadertoy ports explanatory markdown docs

[alphastrata]

whatchu want?
Currently the shaders are 'versioned' when one hits spacebar, which is nice as it gives us a screenshot and the shader code actual etc etc, but it'd be cool if in addition to that it created a markdown doc, put that image into it and added the code as a snippet (rather than the code duplication that we have now...).

A good example of this is already in the screenshots/lines/screenshot.md, this would be a nicer way for us to store these shader ports in a way that makes them more explore-able/discoverable.