Issue 3031 - Add Adblock Browser section to First Run Page (localization)

locale/en-GB/firstRun.json

 {
   "firstRun_acceptableAdsExplanation": {
     "message": "We'd like to encourage websites to use straightforward, unobtrusive advertising. That's why we've established <a>strict guidelines</a> to identify acceptable ads, which are shown under default settings. If you still wish to block every ad you can <a>disable</a> this in a few seconds."
   },
   "firstRun_acceptableAdsHeadline": {
     "message": "Annoying ads will now be blocked"
   },
   "firstRun_contributor_credits": {
     "message": "Contributor Credits"
   },
@@ skipping 41 matching lines @@
   },
   "firstRun_title": {
     "message": "Adblock Plus has been installed"
   },
   "firstRun_toggle_off": {
     "message": "OFF"
   },
   "firstRun_toggle_on": {
     "message": "ON"
   }
-}
+}