Add C# implementation

[papsl]

A very straightforward implementation without any external libraries, that is why also trivial Assert is implemented. I'm lookign for optimal way to run cs samples files without .NET project files etc.

[otobrglez]

Thank you @papsl for your time and contribution I appreciate it!

Hope you don't mind me moving your code into a folder and "packaging" it as .NET console project so that it can be ran with dotnet CLI. I haven't done C# for more than a decade so if you want to improve this or add additional variations or whatever, please feel free to do so.

Thanks again!

P.s.: PR with amendments that was merged