Add javascript-client-sdk to nix config. (#3971)

* Add JavaScript SDK unit tests to CI/hydra via nix environment
* Update Nix environment to handle node.js/npm and OpenAPI dependencies

Co-authored-by: Rob Bearman <robbear@hyperfine.com>
Co-authored-by: helmi.nour <helmiinour@gmail.com>

Author: 3 people

client/default.nix

@@ -0,0 +1,17 @@
+# This file has been generated by node2nix 1.8.0. Do not edit!
+
+{pkgs ? import <nixpkgs> {
+    inherit system;
+  }, system ? builtins.currentSystem, nodejs ? pkgs."nodejs-14_x"}:
+
+let
+  nodeEnv = import ./node-env.nix {
+    inherit (pkgs) stdenv python2 utillinux runCommand writeTextFile;
+    inherit nodejs;
+    libtool = if pkgs.stdenv.isDarwin then pkgs.darwin.cctools else null;
+  };
+in
+import ./node-packages.nix {
+  inherit (pkgs) fetchurl fetchgit;
+  inherit nodeEnv;
+}