Fix Node memory build

Author: schmidt-sebastian

packages/firestore/rollup.config.node.memory.js

@@ -28,7 +28,16 @@ export default [
       format: 'es',
       sourcemap: true
     },
-    plugins: util.es2017Plugins('node'),
+    plugins: [
+      ...util.es2017Plugins('node'),
+      // Needed as we also use the *.proto files
+      copy({
+        assets: ['./src/protos']
+      }),
+      replace({
+        'process.env.FIRESTORE_PROTO_ROOT': JSON.stringify('src/protos')
+      })
+    ],
     external: util.resolveNodeExterns
   },
   {