Remove dependency to System.Drawing for cross-platform compatibility

[philippjbauer]

System.Drawing is only supported in Windows environments.

This PR replaced the Color class from System.Drawing with a standalone implementation and removes the System.Drawing usings.

The IDE formatted some code that slipped into the PR.

[thomasjo]

@philippjbauer This is awesome stuff, thanks!

I haven't had time to test this out yet, in part because I don't work with .NET these days and haven't got a dev environment readily available. Unfortunately, I haven't got CI/CD setup for this project, and the test suite is severely lacking anyway, which means both testing and pushing a new release to NuGet will have to be done manually 😞

Before I get around to testing and releasing a new version, do you think you could push a commit that ensures the code matches the existing formatting? That saves me from having to do it myself, but if you haven't got the time or interest I can take care of it — no worries 😄

Thanks again for helping out this weird, little project!

[philippjbauer]

Hey @thomasjo,

glad to help out. I got quite busy with other responsibilities and don't have time for it unfortunately.

[horvay]

I guess it never got pushed, eh? :D