Enhance Documentation for Response and Error Handling in SDK (#734)

This pull request updates the README and example projects to include
detailed instructions on how to retrieve headers and HTTP status codes
from API responses. Additionally, it outlines methods for capturing HTTP
status codes, headers, and error details when an error occurs. These
enhancements aim to improve the developer's understanding and handling
of API interactions and error management within the line-bot-sdk-nodejs.

(this depends on #733)

Author: Yang-33

docs/guide/client.md

@@ -70,14 +70,32 @@ if (event.type === 'message') {
 For more detail of building webhook and retrieve event objects, please refer to
 its [guide](./webhook.md).
 
+## How to get response header and HTTP status code
+You may need to store the ```x-line-request-id``` header obtained as a response from several APIs.
+In this case, please use ```~WithHttpInfo``` functions. You can get headers and status codes.
+The ```x-line-accepted-request-id``` or ```content-type``` header can also be obtained in the same way.
+
+``` js
+client
+  .replyMessageWithHttpInfo({
+    replyToken: replyToken,
+    messages: [message]
+  })
+  .then((response) => {
+    console.log(response.httpResponse.headers.get('x-line-request-id'));
+    console.log(response.httpResponse.status);
+  });
+```
+
 ## Error handling
 
 There are 4 types of errors caused by client usage.
 
 - `RequestError`: A request fails by, for example, wrong domain or server
   refusal.
 - `ReadError`: Reading from a response pipe fails.
-- `HTTPError`: Server returns a non-2xx response.
+- `HTTPFetchError`: Server returns a response with non-2xx HTTP status code.
+  - (`HTTPError`: You get this error when you use deprecated client. This is not used in the maintained clients.)
 - `JSONParseError`: JSON parsing fails for response body.
 
 For methods returning `Promise`, you can handle the errors
@@ -92,8 +110,10 @@ client
     messages: [message]
    })
   .catch((err) => {
-    if (err instanceof HTTPError) {
+    if (err instanceof HTTPFetchError) {
       console.error(err.statusCode);
+      console.error(err.headers.get('x-line-request-id'));
+      console.error(err.body);
     }
   });
 

examples/echo-bot-ts/index.ts

@@ -6,6 +6,7 @@ import {
   middleware,
   MiddlewareConfig,
   webhook,
+  HTTPFetchError,
 } from '@line/bot-sdk';
 import express, {Application, Request, Response} from 'express';
 
@@ -76,7 +77,11 @@ app.post(
         try {
           await textEventHandler(event);
         } catch (err: unknown) {
-          if (err instanceof Error) {
+          if (err instanceof HTTPFetchError) {
+            console.error(err.statusCode);
+            console.error(err.headers.get('x-line-request-id'));
+            console.error(err.body);
+          } else if (err instanceof Error) {
             console.error(err);
           }
 
@@ -88,7 +93,7 @@ app.post(
       })
     );
 
-    // Return a successfull message.
+    // Return a successful message.
     return res.status(200).json({
       status: 'success',
       results,