A blank line should exist before and after every code block for author readability.

Author: Hosna Khoshkhoo

docs/backend/control-panels.md

@@ -16,10 +16,12 @@ To add a control panel to your add-on, you can use [`plonecli`](https://pypi.org
 ```shell
 plonecli add controlpanel
 ```
+
 This will create the control panel Python file in the control panel's folder where you can define your control panel schema fields. 
 
 ## Registering a Control panel
 To manually register a view as a control panel, add the following registration to your `/profiles/default/controlpanel.xml`.
+
 ```xml
   <?xml version="1.0"?>
   <object