ZX-DB11 doorbell: add ringing sensor

Issue #763

custom_components/tuya_local/devices/zx_db11_doorbell_alarm.yaml

@@ -266,6 +266,20 @@ secondary_entities:
             value: false
           - dps_val: false
             value: true
+  entity: binary_sensor
+  name: Ringing
+  class: sound
+  category: diagnostic
+  dps:
+    - id: 26
+      type: boolean
+      name: sensor
+      optional: true
+      persist: false
+      mapping:
+        - dps_val: null
+          value: false
+        - value: true
   - entity: switch
     name: Doorbell notify
     icon: "mdi:bell-badge"