clean state cache in 30 seconds

src/background/caches.ts

@@ -11,5 +11,12 @@ export class Caches {
     setState(name: string, content: string) {
         this._state = content;
         logger.info(`State (${name}) recieved. To load it: some_var = new Extractor().load()`);
+        // clear cache in 30 seconds
+        setTimeout(() => {
+            if (this._state) {
+                logger.info(`Uploaded state is cleaned after 30 second.`);
+                this._state = "";
+            }
+        }, 30000);
     }
 }