Fix Node build

Author: schmidt-sebastian

packages/firestore/externs.json

@@ -9,6 +9,7 @@
     "node_modules/typescript/lib/lib.es2015.symbol.wellknown.d.ts",
     "node_modules/typescript/lib/lib.es2015.core.d.ts",
     "node_modules/typescript/lib/lib.es2017.object.d.ts",
+    "node_modules/@types/node/base.d.ts",
     "packages/app-types/index.d.ts",
     "packages/app-types/private.d.ts",
     "packages/auth-interop-types/index.d.ts",

packages/firestore/package.json

@@ -46,6 +46,7 @@
     "@firebase/app-types": "0.x"
   },
   "devDependencies": {
+    "@types/node": "8.10.59",
     "protobufjs": "6.8.8",
     "rollup": "1.28.0",
     "rollup-plugin-copy-assets": "1.1.0",

packages/firestore/rollup.config.js

@@ -106,7 +106,7 @@ const es5Builds = [
     ],
     plugins: es5BuildPlugins,
     external: id => deps.some(dep => id === dep || id.startsWith(`${dep}/`))
-  },
+  }
 ];
 
 /**