Add rgbct and color_temperature light platforms (#2138)

Co-authored-by: Oxan van Leeuwen <oxan@oxanvanleeuwen.nl>

esphome/components/cwww/light.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome.components import light, output
 from esphome.const import (
+    CONF_CONSTANT_BRIGHTNESS,
     CONF_OUTPUT_ID,
     CONF_COLD_WHITE,
     CONF_WARM_WHITE,
@@ -12,8 +13,6 @@ from esphome.const import (
 cwww_ns = cg.esphome_ns.namespace("cwww")
 CWWWLightOutput = cwww_ns.class_("CWWWLightOutput", light.LightOutput)
 
-CONF_CONSTANT_BRIGHTNESS = "constant_brightness"
-
 CONFIG_SCHEMA = cv.All(
     light.RGB_LIGHT_SCHEMA.extend(
         {