feed: reduce and censor content that has many newlines

Render newlines as linebreaks is nice, but it can be abused by
adding too many newlines. This change reduces 3 newlines to 2
globally to keep the output somewhat sane.

@@ -157,3 +157,3 @@
   const {host, img, isReply, name, replies, time, userName} = getMetadata(evt, relay);
   const isLongContent = evt.content.trimRight().length > 280;
-  const content = isLongContent ? evt.content.slice(0, 280) : evt.content;
+  const content = (isLongContent ? evt.content.slice(0, 280) : evt.content).replaceAll(/\n{3,}/g, '\n\n');