Update hydrotherm_dynamic_x8_water_heaterv6.yaml

Use inlet temperature sensor as current_temperature state attribute for the water heater, for easier reference/visibility in HA. 

(Currently tested to be working well in my install.)

custom_components/tuya_local/devices/hydrotherm_dynamic_x8_water_heaterv6.yaml

@@ -35,6 +35,9 @@ primary_entity:
         min: 15
         max: 75
       unit: C
+    - id: 21
+      type: integer
+      name: current_temperature
     - id: 7
       type: boolean
       name: away_mode