migrate to typescript, with fixes

src/background/caches.ts

@@ -0,0 +1,15 @@
+import { logger } from "./common";
+
+export class Caches {
+    private _state: string = "";
+    constructor() { }
+    get state(): string {
+        let s = this._state;
+        this._state = "";
+        return s;
+    }
+    setState(name: string, content: string) {
+        this._state = content;
+        logger.info(`State (${name}) recieved. To load it: some_var = new Extractor().load()`);
+    }
+}