Add Nick Janetakis' notes script

https://github.com/nickjj/notes
https://nickjanetakis.com/blog/organize-your-text-based-notes-from-the-command-line-with-this-script

nix/pkgs/notes.nix

@@ -0,0 +1,21 @@
+{ pkgs, ... }:
+
+pkgs.stdenv.mkDerivation rec {
+  pname = "notes";
+  version = "0.3.0";
+
+  src = pkgs.fetchFromGitHub {
+    owner = "nickjj";
+    repo = "notes";
+    rev = "v${version}";
+    sha256 = "gyrsTWPT8w4DsRim3jlbjvpXwX/y+7SwLaM+3LVOJdU=";
+  };
+
+  buildInputs = with pkgs; [ bash ];
+
+  installPhase = ''
+    mkdir -p $out/bin
+    cp $src/notes $out/bin/notes
+    chmod +x $out/bin/notes
+  '';
+}