Add option to enable the 'SMEI_SORT_DIRECTION' experiment

This option, when enabled, activates the SMEI_SORT_DIRECTION experiment,
which is disabled by default in the Community Console.

This experiment lets user set the sort direction in thread lists, so
threads can be ordered in ascending or descending order.

Fixes: #25
Change-Id: Ie8f6825e70d11ee7d3e20a38a7f20e2a34780d9f
diff --git a/src/_locales/en/messages.json b/src/_locales/en/messages.json
index ab740c1..65b2640 100644
--- a/src/_locales/en/messages.json
+++ b/src/_locales/en/messages.json
@@ -91,6 +91,10 @@
     "message": "Add the option to lock multiple threads from the Community Console thread list.",
     "description": "Feature checkbox in the options page"
+  "options_smei_sortdirection": {
+    "message": "Enable the <code class=\"help\" title=\"This experiment lets you sort the Community Console thread list in ascending or descending order.\">SMEI_SORT_DIRECTION</code> experiment.",
+    "description": "Feature checkbox in the options page"
+  },
   "options_profileindicator_header": {
     "message": "Indicator dot",
     "description": "Heading for the profile indicator feature options"