fix (abalon_bcm700d_curtain): add current_position as position mirror

Issue #4358

custom_components/tuya_local/devices/abalon_bcm700d_curtain.yaml

@@ -16,6 +16,9 @@ entities:
         range:
           min: 0
           max: 100
+      - id: 101
+        name: current_position
+        type: integer
       - id: 102
         name: control
         type: string