Add variant setget members for OK HSV and OK HSL

I want to be able to convert both ways. I added these for OK HSL too for consistency; they already existed for standard HSV.
It'd be more efficient to also have methods for getting HSV / OK HSV / OK HSL in one go instead of having to use these separate members, but that might be a bit out of scope for this PR.
C# does have a ToHsv method, so I guess the APIs don't have to be identical.
I should probably add ToOkHsv and ToOkHsl methods though, so C# at least has access to the same functionality as GDScript.
I believe I did the documentation correctly this time around.

core/variant/variant_setget.cpp

@@ -139,6 +139,14 @@ void register_named_setters_getters() {
 	REGISTER_MEMBER(Color, h);
 	REGISTER_MEMBER(Color, s);
 	REGISTER_MEMBER(Color, v);
+
+	REGISTER_MEMBER(Color, ok_hsv_h);
+	REGISTER_MEMBER(Color, ok_hsv_s);
+	REGISTER_MEMBER(Color, ok_hsv_v);
+
+	REGISTER_MEMBER(Color, ok_hsl_h);
+	REGISTER_MEMBER(Color, ok_hsl_s);
+	REGISTER_MEMBER(Color, ok_hsl_l);
 }
 
 void unregister_named_setters_getters() {

doc/classes/Color.xml

@@ -511,6 +511,24 @@
 		<member name="h" type="float" setter="" getter="" default="0.0">
 			The HSV hue of this color, on the range 0 to 1.
 		</member>
+		<member name="ok_hsl_h" type="float" setter="" getter="" default="0.0">
+			The OK HSL hue of this color, on the range 0 to 1.
+		</member>
+		<member name="ok_hsl_l" type="float" setter="" getter="" default="0.0">
+			The OK HSL lightness of this color, on the range 0 to 1.
+		</member>
+		<member name="ok_hsl_s" type="float" setter="" getter="" default="0.0">
+			The OK HSL saturation of this color, on the range 0 to 1.
+		</member>
+		<member name="ok_hsv_h" type="float" setter="" getter="" default="0.0">
+			The OK HSV hue of this color, on the range 0 to 1.
+		</member>
+		<member name="ok_hsv_s" type="float" setter="" getter="" default="0.0">
+			The OK HSV saturation of this color, on the range 0 to 1.
+		</member>
+		<member name="ok_hsv_v" type="float" setter="" getter="" default="0.0">
+			The OK HSV value (brightness) of this color, on the range 0 to 1.
+		</member>
 		<member name="r" type="float" setter="" getter="" default="0.0">
 			The color's red component, typically on the range of 0 to 1.
 		</member>