[gimp-web/testing] Add screenshot for extensions WIP.

[Jehan <jehanp src gnome org>]

commit 1803d8c93b1a02e4f12331691ad22e0e4f163681
Author: Jehan <jehan girinstud io>
Date:   Thu Aug 16 19:31:27 2018 +0200

    Add screenshot for extensions WIP.

 .../gimp-2-10-6-ongoing-dev-extensions.jpg              | Bin 0 -> 44479 bytes
 content/news/2018-08_GIMP-2.10.6_Released/index.md      |   8 +++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/content/news/2018-08_GIMP-2.10.6_Released/gimp-2-10-6-ongoing-dev-extensions.jpg 
b/content/news/2018-08_GIMP-2.10.6_Released/gimp-2-10-6-ongoing-dev-extensions.jpg
new file mode 100644
index 00000000..d20f3df8
Binary files /dev/null and b/content/news/2018-08_GIMP-2.10.6_Released/gimp-2-10-6-ongoing-dev-extensions.jpg 
differ
diff --git a/content/news/2018-08_GIMP-2.10.6_Released/index.md 
b/content/news/2018-08_GIMP-2.10.6_Released/index.md
index 65225678..26e2cf40 100644
--- a/content/news/2018-08_GIMP-2.10.6_Released/index.md
+++ b/content/news/2018-08_GIMP-2.10.6_Released/index.md
@@ -216,7 +216,13 @@ by anyone. The end goal would be to allow creators of such extensions to
 upload them on public repositories, and for anyone to search and install
 them in a few clicks, with version management, updates, etc.
 
-TODO: screenshot.
+<figure>
+<img src="{attach}gimp-2-10-6-ongoing-dev-extensions.jpg"
+     alt="Extension (Ongoing development)">
+<figcaption>
+Extension manager in future GIMP
+</figcaption>
+</figure>
 
 We remind that pippin and Jehan are able to work on GEGL and GIMP thanks
 to crowdfunding. Anyone wishing to participate to their funding is