[gnome-builder] license: Add COPYING to data/icons directory.

[Christian Hergert <chergert src gnome org>]

commit 240995ddf93e444c5b892f0d2b0df0f449abe1c4
Author: Christian Hergert <christian hergert me>
Date:   Thu Sep 11 13:03:11 2014 -0700

    license: Add COPYING to data/icons directory.
    
    We are using CC-by-SA 3 for icon licenses.

 data/icons/COPYING |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/data/icons/COPYING b/data/icons/COPYING
new file mode 100644
index 0000000..2f789c3
--- /dev/null
+++ b/data/icons/COPYING
@@ -0,0 +1,6 @@
+The icons here are licensed under the CC-by-SA 3. You can find the full text of
+the license at:
+
+  http://creativecommons.org/licenses/by-sa/3.0/
+
+See git commit's for authors and contributors to individual icons.