Keyun RGB fan: Add target range to color_temp

Color temp is not automatically scaled, as the target range may be different
for different lights.

Issue #1628

custom_components/tuya_local/devices/keyun_rgb_ceilingfan.yaml

@@ -59,6 +59,10 @@ secondary_entities:
         range:
           min: 0
           max: 1000
+        mapping:
+          - target_range:
+              min: 3000
+              max: 6000
       - id: 24
         name: rgbhsv
         type: hex