fix /api/hits edge caching

app/notes/[slug]/counter.tsx

@@ -7,6 +7,11 @@ const HitCounter = async ({ slug }: { slug: string }) => {
   await connection();
 
   try {
+    // if this is a new slug, redis will automatically create a new key and set its value to 0 (and then 1, obviously)
+    // https://upstash.com/docs/redis/sdks/ts/commands/string/incr
+    // TODO: maybe don't allow this? or maybe it's fine? kinda unclear how secure this is:
+    // https://nextjs.org/blog/security-nextjs-server-components-actions
+    // https://nextjs.org/docs/app/building-your-application/rendering/server-components
     const hits = await redis.incr(slug);
 
     // we have data!