Add option to reposition the expand thread button (CC)

This option repositions the expand thread button all the way to the left
of the thread element in thread lists (Community Console). Originally,
this button is shown in the right.

Requested at pekb/thread/67965396?msgid=91547227.

Change-Id: I10cd62998f6165ec58705fd912089119a7e0a108
diff --git a/src/_locales/en/messages.json b/src/_locales/en/messages.json
index 407ba5c..f3b71d3 100644
--- a/src/_locales/en/messages.json
+++ b/src/_locales/en/messages.json
@@ -99,6 +99,10 @@
     "message": "Show the announcements notification dot more prominently in the Community Console.",
     "description": "Feature checkbox in the options page"
+  "options_repositionexpandthread": {
+    "message": "Place the \"expand thread\" button all the way to the left in the Community Console thread lists.",
+    "description": "Feature checkbox in the options page"
+  },
   "options_profileindicator_header": {
     "message": "Indicator dot",
     "description": "Heading for the profile indicator feature options"