Add NixOS/nixpkgs, update brew link to https

index.md

@@ -84,7 +84,9 @@ You can try it now using Docker:
 * On <a href="https://openbsd.org">OpenBSD</a> based systems:<br/>
 `pkg_add diffoscope`
 
-* On <a href="http://brew.sh/">Homebrew</a>:<br/>`brew install diffoscope`
+* On <a href="https://nixos.org/">NixOS/nixpkgs</a>:<br/>`nix-shell -p diffoscope`
+
+* On <a href="https://brew.sh/">Homebrew</a>:<br/>`brew install diffoscope`
 
 * <a href="/archive">Source tarballs</a>