add is_wrgb to esp32_rmt_led_strip (#3590)

Author: mhetzi

components/light/esp32_rmt_led_strip.rst

@@ -44,6 +44,7 @@ Configuration variables
     - ``BRG``
 
 - **is_rgbw** (*Optional*, boolean): Set to ``true`` if the strip is RGBW. Defaults to ``false``.
+- **is_wrgb** (*Optional*, boolean): Set to ``true`` if the strip is WRGB. Defaults to ``false``.
 - **max_refresh_rate** (*Optional*, :ref:`config-time`):
   A time interval used to limit the number of commands a light can handle per second. For example
   16ms will limit the light to a refresh rate of about 60Hz. Defaults to sending commands as quickly as