Move d3 to package.json and include I18n JS library though Gemfile

Also, update bundle to make it installable again (a version had been removed)

app/assets/javascripts/application.js

@@ -13,9 +13,10 @@
 //= require jquery_ujs
 //= require turbolinks
 //= require pagedown_bootstrap
-//= require d3
 //= require rails-timeago
 //= require locales/jquery.timeago.de.js
+//= require i18n
+//= require i18n/translations
 //
 // lib/assets
 //= require flash

app/javascript/packs/application.js

@@ -13,7 +13,9 @@ import 'bootstrap/dist/js/bootstrap.bundle.min';
 import 'chosen-js/chosen.jquery';
 import 'jstree';
 import 'underscore';
+import 'd3'
 window._ = _; // Publish underscore's `_` in global namespace
+window.d3 = d3; // Publish d3 in global namespace
 
 // CSS
 import 'chosen-js/chosen.css';

app/views/layouts/application.html.slim

@@ -14,6 +14,9 @@ html lang='en'
     = yield(:head)
     = csrf_meta_tags
     = timeago_script_tag
+    script type="text/javascript"
+      | I18n.defaultLocale = "#{I18n.default_locale}";
+      | I18n.locale = "#{I18n.locale}";
   body
     - unless @embed_options[:hide_navbar]
       nav.navbar.navbar-dark.bg-dark.navbar-expand-md.mb-4.py-1 role='navigation'