[webhook] Allow enabling/disabling webhook auto-open

Feature:

  Currently, if the constructor option 'options.webHook' is passed,
  the bot opens the webHook immediately! There's NO way to disable
  this behavior, which might be useful in cases such as:

  * providing custom webhook parameters without opening the webhook
    immediately

  The new boolean option, 'autoOpen', can now be used to control this
  behavior. For example,

  ```js
  const bot = new TelegramBot(token, {
    webHook: {
      autoOpen: false,
    },
  });
  ```

  If set to 'false', the bot does NOT open the web-hook immediately.
  Currently, there's NO way to open the web-hook in this case.
  I'm working on that. Expect a feature to add a method to open
  the web-hook manually!

  If not provided, its value defaults to 'true'.

Implementation:

  * Backwards-compatible: the behavior of opening the web-hook
    immediately remains, when the parameter is NOT provided.

README.md

@@ -130,6 +130,7 @@ Emits `message` when a message arrives.
 | [options.webHook.port] | <code>Number</code> | <code>8443</code> | Port to bind to |
 | [options.webHook.key] | <code>String</code> |  | Path to file with PEM private key for webHook server. (Read synchronously!) |
 | [options.webHook.cert] | <code>String</code> |  | Path to file with PEM certificate (public) for webHook server. (Read synchronously!) |
+| [options.webHook.autoOpen] | <code>Boolean</code> | <code>true</code> | Open webHook immediately |
 | [options.onlyFirstMatch] | <code>Boolean</code> | <code>false</code> | Set to true to stop after first match. Otherwise, all regexps are executed |
 | [options.request] | <code>Object</code> |  | Options which will be added for all requests to telegram api. See https://github.com/request/request#requestoptions-callback for more information. |
 

src/telegram.js

@@ -48,6 +48,7 @@ class TelegramBot extends EventEmitter {
    * @param {Number} [options.webHook.port=8443] Port to bind to
    * @param {String} [options.webHook.key] Path to file with PEM private key for webHook server. (Read synchronously!)
    * @param {String} [options.webHook.cert] Path to file with PEM certificate (public) for webHook server. (Read synchronously!)
+   * @param {Boolean} [options.webHook.autoOpen=true] Open webHook immediately
    * @param {Boolean} [options.onlyFirstMatch=false] Set to true to stop after first match. Otherwise, all regexps are executed
    * @param {Object} [options.request] Options which will be added for all requests to telegram api. See https://github.com/request/request#requestoptions-callback for more information.
    * @see https://core.telegram.org/bots/api
@@ -67,7 +68,10 @@ class TelegramBot extends EventEmitter {
     }
 
     if (options.webHook) {
-      this._WebHook = new TelegramBotWebHook(token, options.webHook, this.processUpdate.bind(this));
+      const autoOpen = options.webHook.autoOpen;
+      if (typeof autoOpen === 'undefined' || autoOpen === true) {
+        this._WebHook = new TelegramBotWebHook(token, options.webHook, this.processUpdate.bind(this));
+      }
     }
   }