(docs) update README with correct package name (#700)

Author: cyrilletuzi

modules/ng-express-engine/README.md

@@ -4,11 +4,13 @@ This is an Express Engine for running Angular Apps on the server for server side
 
 ## Usage
 
+`npm install @nguniversal/express-engine --save`
+
 To use it, set the engine and then route requests to it
 
 ```ts
 import * as express from 'express';
-import { ngExpressEngine } from '@universal/ng-express-engine';
+import { ngExpressEngine } from '@nguniversal/express-engine';
 
 // Set the engine
 app.engine('html', ngExpressEngine({
@@ -60,7 +62,7 @@ You can access them by @Inject
 
 ```ts
 import { Request } from 'express';
-import { REQUEST } from '@universal/ng-express-engine';
+import { REQUEST } from '@nguniversal/express-engine';
 
 @Injectable()
 export class RequestService {