Add number entity to Russound RIO (#39657)

source/_integrations/russound_rio.markdown

@@ -9,6 +9,7 @@ ha_domain: russound_rio
 ha_platforms:
   - diagnostics
   - media_player
+  - number
 ha_codeowners:
   - '@noahhusby'
 ha_config_flow: true
@@ -57,6 +58,14 @@ This integration follows standard integration removal. No extra steps are requir
 
 {% include integrations/remove_device_service.md %}
 
+## Available configuration entities
+
+The integration provides a few entities to configure the device settings. The following entities are supported:
+
+- Bass and Treble
+- Balance
+- Turn on volume
+
 ## Troubleshooting
 
 ### There is a delay on getting the current status