Add documentation for Enmax (virtual integration) (#28927)

source/_integrations/enmax.markdown

@@ -0,0 +1,20 @@
+---
+title: Enmax Energy
+description: Get energy usage from Enmax Energy using the Opower integration
+ha_category:
+  - Energy
+  - Sensor
+ha_release: '2023.10'
+ha_domain: enmax
+ha_integration_type: virtual
+ha_supporting_domain: opower
+ha_supporting_integration: Opower
+ha_codeowners:
+  - '@tronikos'
+ha_config_flow: true
+ha_platforms:
+  - sensor
+ha_iot_class: Cloud Polling
+---
+
+{% include integrations/supported_brand.md %}