Update README setItem chart

Author: aaronshaf

README.md

@@ -112,10 +112,16 @@ export const queryClient = new QueryClient({
 
 ```mermaid
 flowchart TD
-    Application([Client app]) --> |".setItem()"| IDBCache[[IDBCache]]
-    IDBCache -.-> |"Unencrypted chunks"| WebWorker{{Web Worker}}
-    WebWorker -.-> |"Encrypted chunks"| IDBCache
-    IDBCache -.-> |"Encrypted chunks"| IndexedDB[(IndexedDB)]
+ subgraph Browser["Browser"]
+        IDBCache[["IDBCache"]]
+        Application(["Client app"])
+        WebWorker{{"Web Worker"}}
+        IndexedDB[("IndexedDB")]
+  end
+    Application -- ".setItem()" --> IDBCache
+    IDBCache -. Unencrypted chunks .-> WebWorker
+    WebWorker -. Encrypted chunks .-> IDBCache
+    IDBCache -. Encrypted chunks .-> IndexedDB
 ```
 
 ### getItem