Dimming lightbulb: add timer dp.

Based on the feature list of the Arlec and Deta bulbs listed under
products, they also support timers, most likely on the standard
lightbulb template dp 26, but just in case, the dp is made optional.

PR #1500

custom_components/tuya_local/devices/dimming_lightbulb.yaml

@@ -4,6 +4,8 @@ products:
     name: Deta Grid Connect Smart 18W 1900lm Daylight T8 Tube DET018HA
   - id: vjapigi170njdq09
     name: Arlec Smart 4W 380lm Candle Dimmable Bulb GLD060HA
+  - id: aok3caeleulg1neh
+    name: S10 wireless dimmer
 primary_entity:
   entity: light
   dps:
@@ -18,3 +20,20 @@ primary_entity:
         max: 1000
       mapping:
         - scale: 3.92
+secondary_entities:
+  - entity: number
+    name: Timer
+    category: config
+    icon: "mdi:timer"
+    dps:
+      - id: 26
+        type: integer
+        name: value
+        unit: min
+        optional: true
+        range:
+          min: 0
+          max: 86400
+        mapping:
+          - scale: 60
+            step: 60