Add notifications.

web/src/App.tsx

@@ -213,7 +213,7 @@ export default function App() {
 
   // The parsed diff lives here rather than in DiffView because the comments rail
   // needs it too: deciding which comments the diff can still place is one
-  // judgement, made once, so the rail and the diff can't disagree about it.
+  // judgment, made once, so the rail and the diff can't disagree about it.
   const parsedFiles = useMemo(() => (payload ? parseDiff(payload.patch) : []), [payload]);
 
   // What each file's diff currently says, digested. Viewed marks are stored
@@ -395,20 +395,20 @@ export default function App() {
   useEffect(() => {
     if (!path || !revision || stale) return;
 
-    let cancelled = false;
+    let canceled = false;
     let busy = false;
 
     const check = async () => {
       // A hidden pane is a pane nobody is reading. It gets checked the moment it
       // comes back instead, which is when the answer matters.
-      if (cancelled || busy || document.hidden) return;
+      if (canceled || busy || document.hidden) return;
       busy = true;
       const seq = reqRef.current;
       try {
         const { revision: now } = await api.revision(ctx, { ignoreWhitespace: ignoreWs });
         // A load that started while this was in flight has already answered the
         // question, with a revision this closure doesn't know about.
-        if (cancelled || seq !== reqRef.current) return;
+        if (canceled || seq !== reqRef.current) return;
         if (now && now !== revision) setStale(now);
       } catch {
         // A failed poll says nothing about the diff — the next one will.
@@ -424,7 +424,7 @@ export default function App() {
     document.addEventListener('visibilitychange', onVisible);
     window.addEventListener('focus', onVisible);
     return () => {
-      cancelled = true;
+      canceled = true;
       window.clearInterval(timer);
       document.removeEventListener('visibilitychange', onVisible);
       window.removeEventListener('focus', onVisible);