Including Async KV API (cloudflare#26646)

Author: Oxyjun

src/content/docs/durable-objects/api/sqlite-storage-api.mdx

@@ -189,6 +189,10 @@ ctx.storage.onNextSessionRestoreBookmark(bookmark);
 
 <Render file="api-sync-kv" product="durable-objects" />
 
+## Asynchronous KV API
+
+<Render file="api-async-kv-legacy" product="durable-objects" />
+
 ## Alarms
 
 <Render file="api-storage-alarms" product="durable-objects" />