Add C# examples to High-level Multiplayer documentation

[ShawnHardern]

Adds C# examples to High-level Multiplayer documentation

[raulsntos]

Thanks for contributing to the .NET documentation!

I made a few comments regarding consistency with the GDScript code and C# code-style. I have not tested that the code works, but as long as it's equivalent to the GDScript I assume it does. I have, however, tested whether it compiles successfully.

[ShawnHardern]

Thanks for contributing to the .NET documentation!

I made a few comments regarding consistency with the GDScript code and C# code-style. I have not tested that the code works, but as long as it's equivalent to the GDScript I assume it does. I have, however, tested whether it compiles successfully.

Hey @raulsntos thanks so much for the review 🥳, I did copy most of it from a working implementation of that lobby example I did in c# 😁 will add suggested changes

[ShawnHardern]

updated references to _playerInfo and access modifiers 👍🏻

[raulsntos]

Looks good to me, thanks!

[AThousandShips]

Thanks!

[mhilbrunner]

Cherry-picked to 4.3 in #10038.