[babl] extensions/HSL: add model doc string

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 0794559b21fc6ed4080fed602205b00fde05dd72
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Jul 24 15:28:59 2019 +0200

    extensions/HSL: add model doc string

 extensions/HSL.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
---
diff --git a/extensions/HSL.c b/extensions/HSL.c
index 2650a14..0cd1daa 100644
--- a/extensions/HSL.c
+++ b/extensions/HSL.c
@@ -72,17 +72,19 @@ init (void)
   babl_component_new ("lightness", NULL);
   babl_component_new ("alpha", NULL);
 
-  babl_model_new ("name", "HSLA",
+  babl_model_new ("name", "HSL",
+                  "doc", "HSL - Hue Saturation Lightness, an improvement over HSV; which uses lightness; 
defined as (MAX(R,G,B) + MIN(R,G,B))/2 for the grayscale axis; better than HSV, but look into the CIE based 
spaces for better perceptual uniformity. The HSL space is relative to the RGB space associated with the 
format.",
                   babl_component ("hue"),
                   babl_component ("saturation"),
                   babl_component ("lightness"),
-                  babl_component ("alpha"),
-                  "alpha",
                   NULL);
-  babl_model_new ("name", "HSL",
+  babl_model_new ("name", "HSLA",
+                  "doc", "HSL - with separate alpha component.",
                   babl_component ("hue"),
                   babl_component ("saturation"),
                   babl_component ("lightness"),
+                  babl_component ("alpha"),
+                  "alpha",
                   NULL);