switch to jquery 3.3.1 on cdn

app/assets/javascripts/application.js

@@ -1,6 +1,4 @@
 //= require hammer.min.js
-//= require jquery-2.2.4.js
-//= require jquery-migrate-1.4.1.js
 //= require jquery-ui-1.11.2.min.js
 //= require jquery.hotkeys.js
 //= require jquery.timeout.js

app/views/layouts/default.html.erb

@@ -31,6 +31,14 @@
   <% if CurrentUser.user.custom_style.present? %>
     <%= stylesheet_link_tag custom_style_users_path, :media => "screen" %>
   <% end %>
+  <script
+  src="https://code.jquery.com/jquery-3.3.1.min.js"
+  integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8="
+  crossorigin="anonymous"></script>
+  <script
+  src="https://code.jquery.com/jquery-migrate-3.0.1.min.js"
+  integrity="sha256-F0O1TmEa4I8N24nY0bya59eP6svWcshqX1uzwaWC4F4="
+  crossorigin="anonymous"></script>
   <%= javascript_include_tag "application" %>
   <%= raw Danbooru.config.custom_html_header_content %>
   <%= yield :html_header %>