Created Update Handling (markdown)

Update-Handling.md

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+Updates are events that happen in your Telegram account (incoming messages, new channel posts, user name changes, ...) and can be handled by using a callback function, that is, a function called every time an `Update` is received from Telegram.
+
+To set an update handler simply call `set_update_handler` by passing the name of your defined callback function as argument _before_ you start the Client.
+
+Here's a complete example on how to set it up:
+
+``` python
+from pyrogram import Client
+
+
+def callback(update):
+    print(update)
+
+
+client = Client(session_name="example")
+client.set_update_handler(callback)
+
+client.start()
+client.idle()
+```
+
+The last line, `client.idle()` is not strictly necessary but highly recommended; it will block your script execution until you press <kbd>CTRL+C</kbd> and automatically call the `stop` method which stops the Client and gently close the underlying connection.
+
+# Examples
+
+- Echo:
+
+  ``` python
+  def callback(update):
+      if isinstance(update, types.UpdateShortMessage) and not update.out:
+          client.send_message(update.user_id, update.message)
+  ```
+  This checks if the update type is `UpdateShortMessage` and that the update is not generated by yourself (i.e., the message is not outgoing), then sends back the same message.