[gimp-web/testing] news: add link to post explaining HGT and how to map to colors.

[Jehan Pagès <jehanp src gnome org>]

commit 99c0bf3c9126b7707fc4228a5a2bdb93ff5de76b
Author: Jehan <jehan girinstud io>
Date:   Tue Dec 12 05:19:32 2017 +0100

    news: add link to post explaining HGT and how to map to colors.
    
    I just published this post and I feel like it can be useful for people
    wanting to know more since the support is still a bit rough.

 .../news/2017-12-XX GIMP 2.9.8 Released/index.md   |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/content/news/2017-12-XX GIMP 2.9.8 Released/index.md b/content/news/2017-12-XX GIMP 2.9.8 
Released/index.md
index bd14103..c06a421 100644
--- a/content/news/2017-12-XX GIMP 2.9.8 Released/index.md      
+++ b/content/news/2017-12-XX GIMP 2.9.8 Released/index.md      
@@ -168,7 +168,8 @@ more expected results now.
   only 2 variants) which will be imported as grayscale RGB images.
   In order to obtain more visible relief information, you will want to map
   altitudes to colors, for instance with "Gradient Map" filter as we did in the
-  example image below.
+  example image below (see also this [explicative post on the
+  process](https://girinstud.io/news/2017/12/new-format-in-gimp-hgt/)).
 
 <figure>
 <img src="{filename}GIMP-import-hgt.png" alt='Importing HGT files in GIMP' width='950' height='616'>