[chrome-gnome-shell] i18n: added notice for "translation_credits" string

[Yuri Konotopov <ykonotopov src gnome org>]

commit 9a9fc9c72e97db313ac7ce812c08871a95136594
Author: Yuri Konotopov <ykonotopov gmail com>
Date:   Thu Mar 10 20:19:11 2016 +0300

    i18n: added notice for "translation_credits" string

 extension/_locales/en/messages.json |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/extension/_locales/en/messages.json b/extension/_locales/en/messages.json
index e3689dc..35556aa 100644
--- a/extension/_locales/en/messages.json
+++ b/extension/_locales/en/messages.json
@@ -73,7 +73,8 @@
                "message": "About translation"
        },
        "translation_credits": {
-               "message": ""
+               "message": "",
+               "description": "HTML markup enabled for this string."
        },
 
        "hours": {