Docs: Add description limits to cheat sheet

docs/configuration/cheatsheet.md

@@ -18,6 +18,7 @@ To add configuration to your config file, you can copy it from the base config.
 * `notify_email`: Email used for notifications.
 * `description`: The instance’s description, can be seen in nodeinfo and ``/api/v1/instance``.
 * `limit`: Posts character limit (CW/Subject included in the counter).
+* `discription_limit`: The character limit for image descriptions.
 * `chat_limit`: Character limit of the instance chat messages.
 * `remote_limit`: Hard character limit beyond which remote posts will be dropped.
 * `upload_limit`: File size limit of uploads (except for avatar, background, banner).