Add path to version select in guides

When selecting another version of the guide we can append the path to
the version URL. This makes sure someone stays on "Active Record Basics"
guide when switching versions.

Author: p8

guides/rails_guides/generator.rb

@@ -188,6 +188,7 @@ def generate_guide(guide, output_file)
           [@source_dir],
           edge:          @edge,
           version:       @version,
+          path:          output_file,
           epub:          "epub/#{epub_filename}",
           language:      @language,
           direction:     @direction,

guides/source/layout.html.erb

@@ -70,7 +70,7 @@
             <select id="version-switcher-select" class="guides-version">
               <option value="https://edgeguides.rubyonrails.org/"<%= " selected" if @edge %>>Edge</option>
               <% %w[8.0 7.2 7.1 7.0 6.1 6.0 5.2 5.1 5.0 4.2 4.1 4.0 3.2 3.1 3.0 2.3].each do |version| %>
-                <option value="https://guides.rubyonrails.org/v<%= version %>/"<%= " selected" if @version&.start_with?("v#{version}") %>><%= version %></option>
+                <option value="https://guides.rubyonrails.org/v<%= version %>/<%= @path %>"<%= " selected" if @version&.start_with?("v#{version}") %>><%= version %></option>
               <% end %>
             </select>
           </span>