enable caching for comments

themes/hugo-mastodon-comments/static/comments/config.sample.php

@@ -4,5 +4,6 @@ $config = [
     'user-id' => 379833,
     'search-url' => 'https?://fsfe.org', // please use https?:// as schema
     'cache_toots' => 300,
+    'cache_comments' => 300,
     'debug' => true
 ];