Add WebSockets conceptual doc

[greenEkatherine]

Summary

Added WebSockets conceptual doc with examples and tips

Fixes #31759

Preview https://review.learn.microsoft.com/en-us/dotnet/fundamentals/networking/websockets?branch=pr-en-us-32058

[IEvangelist]

This looks good, thank you. We'll when you make the suggested changes. We also need a TOC entry for this article.

[CarnaViire]

Thanks a lot for your work on this!

It would be great if we could also have a fully runnable example on connecting+sending+receiving+closing e.g. with a public echo endpoint (I guess that would only exist for H/1) -- and the code snippets in the article would be parts of that example, like in https://github.com/dotnet/docs/blob/main/docs/fundamentals/networking/sockets/socket-services.md?plain=1#L31 (with code in https://github.com/dotnet/docs/tree/main/docs/fundamentals/networking/snippets/socket).

If that would be hard/take a lot of time to do, let's create a follow-up issue. But I think it's important that the conceptual doc would cover all the lifecycle of a WebSocket, not only connecting.

[greenEkatherine]

We also need a TOC entry for this article.

@IEvangelist should I add it manually or it can be done automatically?

[IEvangelist]

We also need a TOC entry for this article.

@IEvangelist should I add it manually or it can be done automatically?

It needs to be added manually as part of this PR. Where does the new article belong? See TOC for details. Here is probably where you'd likely want to put it, somewhere beneath the other Networking content.

https://github.com/dotnet/docs/blob/main/docs/fundamentals/toc.yml#L2585

[IEvangelist]

Looks good to me, we'll - thank you 🙏