Light string: use string rather than hex for mapped values.

Since we map the values to strings rather than making use of the hex values,
using hex for the type causes decode errors.

Add product details for popotan device

#1171

custom_components/tuya_local/devices/light_string.yaml

@@ -1,4 +1,7 @@
 name: Fairy lights
+products:
+  - id: rqsvgaquywwekm6x
+    name: Popotan Smart Fairy String Lights
 primary_entity:
   entity: light
   dps:
@@ -41,7 +44,7 @@ secondary_entities:
     category: config
     dps:
       - id: 25
-        type: hex
+        type: string
         name: option
         mapping:
           - dps_val: "0103e8"
@@ -78,7 +81,7 @@ secondary_entities:
     icon: "mdi:music"
     dps:
       - id: 101
-        type: hex
+        type: string
         name: option
         mapping:
           - dps_val: 16401bb1006e03e801f4