Update Bootstrap to version 4

app/overrides/add_rich_editor_tab.rb

@@ -2,5 +2,5 @@
   virtual_path: 'spree/admin/shared/sub_menu/_configuration',
   name: 'add_rich_editor_tab',
   insert_bottom: '[data-hook="admin_configurations_sidebar_menu"]',
-  text: '<li<%== " class=\"active\"" if controller.controller_name == "editor_settings" %>><%= link_to Spree.t(:rich_editor), spree.edit_admin_editor_settings_path %></li>'
+  partial: 'spree/admin/editor_settings/rich_editor'
 )

app/views/spree/admin/editor_settings/_rich_editor.html.erb

@@ -0,0 +1,3 @@
+<li class="sidebar-menu-item d-block w-100<%== " selected" if controller.controller_name == "editor_settings" %>">
+    <%= link_to Spree.t(:rich_editor), spree.edit_admin_editor_settings_path, { class: "py-1 px-3 d-block sidebar-submenu-item #{ 'text-success' if controller.controller_name == "editor_settings" }"} %>
+</li>

app/views/spree/admin/editor_settings/edit.html.erb

@@ -14,7 +14,7 @@
               <%= label_tag(:current_editor, Spree.t(:rich_editor_engine)) %>
               <%= select_tag(:current_editor, options_for_select(Spree::EditorSetting.editors, SpreeEditor::Config[:current_editor]), class: 'select2') %>
             </div>
-            <div class="checkbox">
+            <div class="checkbox form-group">
               <%= label_tag(:enabled) do %>
                 <%= preference_field_tag(:enabled, SpreeEditor::Config[:enabled], type: :boolean) %>
                 <%= Spree.t(:enable_rich_editor) %>