update readme with nix setup and disclaimer, increase scale max to 10

shell.nix

@@ -0,0 +1,25 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  lib = import <nixpkgs/lib>;
+  buildNodeJs = pkgs.callPackage "${<nixpkgs>}/pkgs/development/web/nodejs/nodejs.nix" {
+    python = pkgs.python3;
+  };
+
+  nodejsVersion = lib.fileContents ./.nvmrc;
+
+  nodejs = buildNodeJs {
+    enableNpm = true;
+    version = nodejsVersion;
+    sha256 = "032801kg24j04xmf09m0vxzlcz86sv21s24lv9l4cfv08k1c4byp";
+  };
+
+  # Overlay to use custom nodejs for nodePackages
+  customPkgs = pkgs // { inherit nodejs; };
+
+in customPkgs.mkShell {
+  buildInputs = with customPkgs; [
+    nodejs
+    nodePackages."@angular/cli"
+  ];
+}