Add length_seconds to playlist on watch page

src/invidious/mixes.cr

@@ -99,7 +99,10 @@ def template_mix(mix)
     html += <<-END_HTML
       <li class="pure-menu-item">
         <a href="/watch?v=#{video["videoId"]}&list=#{mix["mixId"]}">
-          <img style="width:100%;" src="/vi/#{video["videoId"]}/mqdefault.jpg">
+          <div class="thumbnail">
+              <img class="thumbnail" src="/vi/#{video["videoId"]}/mqdefault.jpg">
+              <p class="length">#{recode_length_seconds(video["lengthSeconds"].as_i)}</p>
+          </div>
           <p style="width:100%">#{video["title"]}</p>
           <p>
               <b style="width: 100%">#{video["author"]}</b>

src/invidious/playlists.cr

@@ -234,7 +234,10 @@ def template_playlist(playlist)
     html += <<-END_HTML
       <li class="pure-menu-item">
         <a href="/watch?v=#{video["videoId"]}&list=#{playlist["playlistId"]}">
-          <img style="width:100%;" src="/vi/#{video["videoId"]}/mqdefault.jpg">
+          <div class="thumbnail">
+              <img class="thumbnail" src="/vi/#{video["videoId"]}/mqdefault.jpg">
+              <p class="length">#{recode_length_seconds(video["lengthSeconds"].as_i)}</p>
+          </div>
           <p style="width:100%">#{video["title"]}</p>
           <p>
               <b style="width: 100%">#{video["author"]}</b>