simple switch with timer: add product id for Teckin SP21

Issue #772

custom_components/tuya_local/devices/simple_switch_timer.yaml

@@ -1,4 +1,7 @@
 name: Simple switch with timer
+products:
+  - id: r15JnoGqWPM4PPtl
+    name: Teckin SP21
 primary_entity:
   entity: switch
   class: outlet