Add explicit ts-node dependency (#2595)

This fixes https://github.com/firebase/firebase-js-sdk/blob/master/packages/firestore/test/unit/generate_spec_json.sh

Author: schmidt-sebastian

packages/firestore/package.json

@@ -35,12 +35,12 @@
     "dist"
   ],
   "dependencies": {
+    "@firebase/component": "0.1.3",
     "@firebase/firestore-types": "1.9.0",
     "@firebase/logger": "0.1.34",
+    "@firebase/util": "0.2.38",
     "@firebase/webchannel-wrapper": "0.2.35",
     "@grpc/proto-loader": "^0.5.0",
-    "@firebase/util": "0.2.38",
-    "@firebase/component": "0.1.3",
     "grpc": "1.24.2",
     "tslib": "1.10.0"
   },
@@ -57,6 +57,7 @@
     "rollup-plugin-replace": "2.2.0",
     "rollup-plugin-terser": "5.1.3",
     "rollup-plugin-typescript2": "0.25.3",
+    "ts-node": "8.5.4",
     "typescript": "3.7.5"
   },
   "repository": {