nip-13: check zero leading bits

before it was only testing if the nonce commitment is high enough
but didn't verify leading zero bits.

with this change rendering checks now the leading zero bits count
of the event id.

src/main.js

@@ -328,7 +328,12 @@ function renderFeed() {
   const sortedFeeds = textNoteList
     // dont render notes from the future
     .filter(note => note.created_at < now)
-    .filter(note => !fitlerDifficulty || note.tags.some(([tag, , commitment]) => tag === 'nonce' && commitment >= fitlerDifficulty))
+    // if difficulty filter is configured dont render notes with too little pow
+    .filter(note => {
+      return !fitlerDifficulty || note.tags.some(([tag, , commitment]) => {
+        return tag === 'nonce' && commitment >= fitlerDifficulty && zeroLeadingBitsCount(note.id) >= fitlerDifficulty;
+      });
+    })
     .sort(sortByCreatedAt).reverse();
   sortedFeeds.forEach((evt, i) => {
     if (feedDomMap[evt.id]) {