nix: add shell.nix

shell.nix

@@ -0,0 +1,27 @@
+{ pkgs ? import <nixpkgs> {}, lib ? pkgs.lib }:
+
+with lib;
+
+let
+  neededLibraries = with pkgs; [
+    curl
+    libxml2
+    libxslt
+  ];
+
+in
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    ruby
+    bundler
+
+    pkg-config
+    shared-mime-info
+    cacert
+  ] ++ neededLibraries;
+
+  "LD_LIBRARY_PATH" = makeLibraryPath neededLibraries;
+  "SSL_CERT_DIR" = "${pkgs.cacert}/etc/ssl/certs";
+  "SSL_CERT_FILE" = "${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt";
+  "FREEDESKTOP_MIME_TYPES_PATH" = "${pkgs.shared-mime-info}/share/mime/packages/freedesktop.org.xml";
+}