feat: Add nixpacks config

nixpacks.json

@@ -0,0 +1,50 @@
+{
+    "providers": [],
+    "buildImage": "ghcr.io/railwayapp/nixpacks:ubuntu-1731369831",
+    "variables": {
+      "CI": "true",
+      "NIXPACKS_METADATA": "node",
+      "NODE_ENV": "production",
+      "NPM_CONFIG_PRODUCTION": "false"
+    },
+    "phases": {
+      "build": {
+        "dependsOn": [
+          "install"
+        ],
+        "cmds": [
+          "yarn run build"
+        ],
+        "cacheDirectories": [
+          "node_modules/.cache"
+        ]
+      },
+      "install": {
+        "dependsOn": [
+          "setup"
+        ],
+        "cmds": [
+          "yarn install --frozen-lockfile"
+        ],
+        "cacheDirectories": [
+          "/usr/local/share/.cache/yarn/v6"
+        ],
+        "paths": [
+          "/app/node_modules/.bin"
+        ]
+      },
+      "setup": {
+        "nixPkgs": [
+          "nodejs_18",
+          "yarn-1_x"
+        ],
+        "nixOverlays": [
+          "https://github.com/railwayapp/nix-npm-overlay/archive/main.tar.gz"
+        ],
+        "nixpkgsArchive": "e05605ec414618eab4a7a6aea8b38f6fbbcc8f08"
+      }
+    },
+    "start": {
+        "cmd": "yarn dev"
+    }
+  }