[babl] extensions/HSV: add documentation for model

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

commit fb5363bd749c7b2fbbe387a9bfa819f84ca76567
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Jul 24 11:47:33 2019 +0200

    extensions/HSV: add documentation for model

 extensions/HSV.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/extensions/HSV.c b/extensions/HSV.c
index 9446b15..aa301e3 100644
--- a/extensions/HSV.c
+++ b/extensions/HSV.c
@@ -102,6 +102,7 @@ models (void)
     babl_component ("value"),
     babl_component ("alpha"),
     "alpha",
+    "doc", "A legacy color model that exists for compatibility with old GIMP code, V is MAX(R,G,B), with 
separate alpha.",
     NULL
   );
 
@@ -110,6 +111,7 @@ models (void)
     babl_component ("hue"),
     babl_component ("saturation"),
     babl_component ("value"),
+    "doc", "A legacy color model that exists for compatibility with old GIMP code, V is MAX(R,G,B).",
     NULL
   );
 }