add i18n

app/views/shared/_navbar_buttons.html.erb

@@ -1,5 +1,5 @@
 <%= link_to Docuseal.multitenant? ? console_redirect_index_path(redir: "#{Docuseal::CONSOLE_URL}/plans") : "#{Docuseal::CLOUD_URL}/sign_up?#{{ redir: "#{Docuseal::CONSOLE_URL}/on_premise" }.to_query}", class: 'hidden md:inline-flex btn btn-warning btn-sm', data: { prefetch: false } do %>
-  Upgrade
+  <%= t('upgrade') %>
 <% end %>
 <% if signed_in? && current_user != true_user %>
   <span class="hidden md:inline-flex h-3 border-r border-base-content"></span>