Add traefik example

examples/traefik/arion-compose.nix

@@ -0,0 +1,28 @@
+{ pkgs, ... }: {
+
+  config.services = {
+    traefik.service = {
+      image = "traefik:v2.4";
+      container_name = "traefik";
+      command = [
+        "--api.insecure=true"
+        "--providers.docker=true"
+        "--providers.docker.exposedbydefault=false"
+        "--entrypoints.web.address=:80"
+      ];
+      ports = [ "80:80" "8080:8080" ];
+      volumes = [ "/var/run/docker.sock:/var/run/docker.sock:ro" ];
+    };
+
+    whoami.service = {
+      image = "traefik/whoami";
+      container_name = "simple-service";
+      labels = {
+        "traefik.enable" = "true";
+        "traefik.http.routers.whoami.rule" = "Host(`whoami.localhost`)";
+        "traefik.http.routers.whoami.entrypoints" = "web";
+      };
+    };
+  };
+}
+

examples/traefik/arion-pkgs.nix

@@ -0,0 +1,6 @@
+# Instead of pinning Nixpkgs, we can opt to use the one in NIX_PATH
+import <nixpkgs> {
+  # We specify the architecture explicitly. Use a Linux remote builder when
+  # calling arion from other platforms.
+  system = "x86_64-linux";
+}