Move Inviqa example from play.tailwindcss.com

tailwindcss/inviqa/flake.nix

@@ -0,0 +1,29 @@
+{
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+  outputs = inputs:
+    let
+      system = "x86_64-linux";
+      pkgs = import inputs.nixpkgs { inherit system; };
+    in
+    {
+      devShells.${system}.default = pkgs.mkShell {
+        packages = with pkgs; [
+          (pkgs.writeShellApplication {
+            name = "serve";
+
+            runtimeInputs = with pkgs; [
+              simple-http-server
+              tailwindcss_3
+            ];
+
+            text = ''
+              simple-http-server --index --nocache "$@" & \
+              tailwindcss --input input.css --output tailwind.css --watch & \
+              wait
+            '';
+          })
+        ];
+      };
+    };
+}