feat: add clear listener methods (#834)

- by @daniel0611

Co-authored-by: Mohammed Sohail <sohailsameja@gmail.com>

src/telegram.js

@@ -1681,6 +1681,13 @@ class TelegramBot extends EventEmitter {
     return this._textRegexpCallbacks.splice(index, 1)[0];
   }
 
+  /**
+   * Remove all listeners registered with `onText()`.
+   */
+  clearTextListeners() {
+    this._textRegexpCallbacks = [];
+  }
+
   /**
    * Register a reply to wait for a message response.
    * @param  {Number|String}   chatId       The chat id where the message cames from.
@@ -1717,6 +1724,13 @@ class TelegramBot extends EventEmitter {
     return this._replyListeners.splice(index, 1)[0];
   }
 
+  /**
+   * Removes all replies that have been prev. registered for a message response.
+   */
+  clearReplyListeners() {
+    this._replyListeners = [];
+  }
+
   /**
    * Use this method to get up to date information about the chat
    * (current name of the user for one-on-one conversations, current