Improve documentation for device_class (#2073)

source/_components/cover.markdown

@@ -11,6 +11,12 @@ footer: true
 
 Home Assistant can give you an interface to control covers such as rollershutters, blinds, and garage doors.
 
+The display style of each entity can be modified in the [customize section](/getting-started/customizing-devices/). The following device classes are supported for covers:
+
+- **None**: Generic cover device
+- **window**: Window controller
+- **garage**: Garage door controller
+
 ## {% linkable_title Services %}
 
 ### {% linkable_title Cover control services %}