Update README.md

README.md

@@ -4,17 +4,17 @@ servant-event-stream
 This library adds necessary type combinators to support [Server Sent Events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events)
 within [Servant ecosystem](https://github.com/haskell-servant/).
 
-Dev Environment
----------------
+Development Environment
+-----------------------
 
-Dev env is based on [Nix](https://nixos.org) and [Niv](https://github.com/nmattia/niv).
+Development environment uses [Nix](https://nixos.org) flakes.
 
 To enter the dev shell, run
 ```bash
-nix-shell
+nix develop
 ```
 
 You can build the project with
 ```bash
-nix-build
-```
+nix build
+```