add(shell): writing a shell in c#

README.md

@@ -355,6 +355,7 @@ It's a great way to learn.
 * [**C**: _Writing a UNIX Shell_](https://indradhanush.github.io/blog/writing-a-unix-shell-part-1/)
 * [**C**: _Build Your Own Shell_](https://github.com/tokenrove/build-your-own-shell)
 * [**C**: Write a shell in C](https://danishpraka.sh/posts/write-a-shell/)
+* [**C#**: _Write a shell in C#_](https://ntk148v.github.io/posts/writing-a-simple-shell-in-c-sharp/)
 * [**Go**: _Writing a simple shell in Go_](https://sj14.gitlab.io/post/2018-07-01-go-unix-shell/)
 * [**Rust**: _Build Your Own Shell using Rust_](https://www.joshmcguigan.com/blog/build-your-own-shell-rust/)