Update docstrings for asynctelebot.

telebot/__init__.py

@@ -73,10 +73,12 @@ class ExceptionHandler:
 
 class TeleBot:
     """
-    This is the main class to deal with bot.
+    This is the main synchronous class for Bot.
+
     It allows you to add handlers for different kind of updates.
 
     Usage:
+
     .. code-block:: python
 
         from telebot import TeleBot

telebot/asyncio_handler_backends.py

@@ -29,3 +29,28 @@ class StatesGroup:
             if not name.startswith('__') and not callable(value) and isinstance(value, State):
                 # change value of that variable
                 value.name = ':'.join((cls.__name__, name))
+
+
+class SkipHandler:
+    """
+    Class for skipping handlers.
+    Just return instance of this class 
+    in middleware to skip handler.
+    Update will go to post_process,
+    but will skip execution of handler.
+    """
+
+    def __init__(self) -> None:
+        pass
+
+class CancelUpdate:
+    """
+    Class for canceling updates.
+    Just return instance of this class 
+    in middleware to skip update.
+    Update will skip handler and execution
+    of post_process in middlewares.
+    """
+
+    def __init__(self) -> None:
+        pass