Add HSV value specification (#2481)

* Update feature_rgblight.md

I got caught out with this as most color pickers use a percentage NOT 0-255 for this number

* Amended description

Woops! Was focused on s/v not being a percentage i got h wrong.

docs/feature_rgblight.md

@@ -92,7 +92,7 @@ rgblight_disable();  // turn all lights off
 rgblight_enable();  // turn lights on, based on their previous state (stored in EEPROM)
 
 rgblight_setrgb(r, g, b);  // where r/g/b is a number from 0..255.  Turns all the LEDs to this color
-rgblight_sethsv(h, s, v);  // HSV color control
+rgblight_sethsv(h, s, v);  // HSV color control - h is a value from 0..360 and s/v is a value from 0..255
 rgblight_setrgb_at(r,g,b, LED);  // control a single LED.  0 <= LED < RGBLED_NUM
 rgblight_sethsv_at(h,s,v, LED);  // control a single LED.  0 <= LED < RGBLED_NUM
 ```