[library-web] add gthumb

[Frederic Peters <fpeters src gnome org>]

commit ec3f1a857acbdb5f7e533d29acd0be30c346df51
Author: Frédéric Péters <fpeters 0d be>
Date:   Sat Aug 27 10:38:51 2016 +0200

    add gthumb

 data/extra-tarballs |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/data/extra-tarballs b/data/extra-tarballs
index cf20e0b..d771836 100644
--- a/data/extra-tarballs
+++ b/data/extra-tarballs
@@ -102,6 +102,7 @@ gnome://glade3?min=3.8
 
 gnome://gnumeric?min=1.12
 gnome://clutter-gtk?min=1.4
+gnome://gthumb?min=2.12
 
 http://www.freedesktop.org/software/geoclue/releases/2.1/geoclue-2.1.1.tar.xz