add index to playlist item

src/invidious/playlists.cr

@@ -545,7 +545,7 @@ def template_playlist(playlist)
   playlist["videos"].as_a.each do |video|
     html += <<-END_HTML
       <li class="pure-menu-item">
-        <a href="/watch?v=#{video["videoId"]}&list=#{playlist["playlistId"]}">
+        <a href="/watch?v=#{video["videoId"]}&list=#{playlist["playlistId"]}&index=#{video["index"]}">
           <div class="thumbnail">
               <img class="thumbnail" src="/vi/#{video["videoId"]}/mqdefault.jpg">
               <p class="length">#{recode_length_seconds(video["lengthSeconds"].as_i)}</p>

src/invidious/views/components/item.ecr

@@ -48,7 +48,7 @@
                 <p dir="auto"><b><%= HTML.escape(item.author) %></b></p>
             </a>
         <% when PlaylistVideo %>
-            <a style="width:100%" href="/watch?v=<%= item.id %>&list=<%= item.plid %>">
+            <a style="width:100%" href="/watch?v=<%= item.id %>&list=<%= item.plid %>&index=<%= item.index %>">
                 <% if !env.get("preferences").as(Preferences).thin_mode %>
                     <div class="thumbnail">
                         <img class="thumbnail" src="/vi/<%= item.id %>/mqdefault.jpg"/>