Create a new sockets tutorial

We have one page in the Framework docs that is sort of like a sockets tutorial, and should be improved if that is its goal:

https://docs.microsoft.com/en-us/dotnet/framework/network-programming/sockets

Otherwise, learning sockets in .NET seems to largely depend on having prior experience in some other platform. I've personally helped a number of people learning sockets in .NET and it seems to be challenging to learn. So, we should create a new tutorial.

We should also pool the team's experience and record some opinions and best practices. Showing patterns like an accept loop or basic buffering/parsing strategies could be helpful.