Add shell.nix file

I have added a shell.nix file that helps setting up the environment for
building if nix is installed.

To use it you can run `nix-shell shell.nix` which will install all the
required dependecies, and then just `make run` should work.

shell.nix

@@ -0,0 +1,42 @@
+{ pkgs ? import (builtins.fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/archive/e7603eba51f2c7820c0a182c6bbb351181caa8e7.zip";
+    sha256 = "sha256:0mwck8jyr74wh1b7g6nac1mxy6a0rkppz8n12andsffybsipz5jw";
+  }) { } }:
+
+let
+  qtCustom = with pkgs.qt515;
+    env "qt-custom-${qtbase.version}" ([
+      qtquickcontrols2
+      qtgraphicaleffects
+      qtbase qttools qtdeclarative
+      qtlottie qtmultimedia
+      qtquickcontrols qtquickcontrols2
+      qtsvg qtwebengine qtwebview
+    ]);
+in pkgs.mkShell {
+  name = "status-desktop-build-shell";
+
+  buildInputs = with pkgs; [
+    qt5Full
+    bash curl wget git file unzip jq lsb-release
+    cmake gnumake pkg-config gnugrep qtCustom
+    go_1_19
+    pcre nss pcsclite extra-cmake-modules
+    xorg.libxcb xorg.libX11 libxkbcommon
+  ] ++ (with gst_all_1; [
+    gst-libav gstreamer
+    gst-plugins-bad  gst-plugins-base
+    gst-plugins-good gst-plugins-ugly
+  ]);
+
+  # Avoid terminal issues.
+  TERM = "xterm";
+  LANG = "en_US.UTF-8";
+  LANGUAGE = "en_US.UTF-8";
+
+  QTDIR = qtCustom;
+
+  shellHook = ''
+    export MAKEFLAGS="-j$NIX_BUILD_CORES"
+  '';
+}