Add js sdk changes

With type declarations and various missing parts added by Willy-JL

applications/system/js_app/packages/fz-sdk/usbdisk/index.d.ts

@@ -0,0 +1,24 @@
+/**
+ * Module for USB mass storage emulation
+ * @version Available with JS feature `usbdisk`
+ * @module
+ */
+
+/**
+ * @brief Start emulating mass storage device
+ * @param path The disk image to emulate
+ */
+export declare function start(path: string): void;
+
+/**
+ * @brief Stop emulating mass storage device
+ */
+export declare function stop(): void;
+
+/**
+ * @brief Check if the mass storage device was exected
+ * 
+ * Useful as a loop condition with a delay, so UsbDisk keeps running until ejected
+ * 
+ */
+export declare function wasEjected(): boolean;