add nancyfx template owner

Author: wing328

README.md

@@ -802,6 +802,7 @@ Here is a list of template creators:
    * TypeScript (Angular2): @roni-frantchi
  * Server Stubs
    * C# ASP.NET5: @jimschubert
+   * C# NancyFX: @mstefaniuk
    * Go Server: @guohuang
    * Haskell Servant: @algas
    * Java Spring Boot: @diyfr