chore: add minor note to index page

src/index.vto

···
       <p>
         <small>
           <strong><i class="ph-fill ph-warning"></i></strong>
-          The items are added to the default "IndexedDB" output, so make sure that output is configured.
+          The items are added to the default "IndexedDB" (local-only) output, so make sure that output is configured.
         </small>
       </p>
     </section>