Issue 5555 - [webextensions] Add a message for Firefox users on the options page

options.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 100 matching lines @@
   {
     getInfo("platform", platform =>
     {
       if (platform == "chromium" && application != "opera")
         application = "chrome";
 
       getDocLink(application + "_support", url =>
       {
         setLinks("found-a-bug", url);
       });
+
+      if (platform == "gecko")
+        $("#firefox-warning").removeAttr("hidden");
     });
   });
 
   // Add event listeners
   $("#updateFilterLists").click(updateFilterLists);
   $("#startSubscriptionSelection").click(startSubscriptionSelection);
   $("#subscriptionSelector").change(updateSubscriptionSelection);
   $("#addSubscription").click(addSubscriptionClicked);
   $("#acceptableAds").click(toggleAcceptableAds);
   $("#whitelistForm").submit(addWhitelistDomain);
@@ skipping 604 matching lines @@
       onFilterMessage(message.action, message.args[0]);
       break;
     case "prefs.respond":
       onPrefMessage(message.action, message.args[0]);
       break;
     case "subscriptions.respond":
       onSubscriptionMessage(message.action, message.args[0]);
       break;
   }
 });