Overhaul example scripts

- all examples depends on the sdk code, contains in the repo.
- Use `/callback` as the endpoint in echo-bot-ts.
- Update various dependencies

Author: tokuhirom

examples/echo-bot-ts/README.md

@@ -26,6 +26,7 @@ cd line-bot-sdk-nodejs/examples/echo-bot-ts
 - Install all dependencies.
 
 ```bash
+npm run build-sdk
 npm install
 ```
 
@@ -40,7 +41,7 @@ export PORT=<YOUR_PORT>
 - Setup your webhook URL in your LINE Official Account to be in the following format. Don't forget to disable the greeting messages and auto-response messages for convenience.
 
 ```bash
-https://example-url.com/webhook
+https://example.com/callback
 ```
 
 - Compile the TypeScript files.

examples/echo-bot-ts/index.ts

@@ -60,12 +60,12 @@ app.get(
 
 // This route is used for the Webhook.
 app.post(
-  '/webhook',
+  '/callback',
   middleware(middlewareConfig),
   async (req: Request, res: Response): Promise<Response> => {
     const events: WebhookEvent[] = req.body.events;
 
-    // Process all of the received events asynchronously.
+    // Process all the received events asynchronously.
     const results = await Promise.all(
       events.map(async (event: WebhookEvent) => {
         try {