Add barcode-detector-api-polyfill dependency and update environment variable declarations in SvelteKit project

node_modules/@zxing/browser/es2015/readers/IBrowserCodeReaderOptions.d.ts

@@ -0,0 +1,8 @@
+export interface IBrowserCodeReaderOptions {
+    /** Delay time between subsequent successful decode results. */
+    delayBetweenScanSuccess?: number;
+    /** Delay time between decode attempts made by the scanner. */
+    delayBetweenScanAttempts?: number;
+    /** Timeout for waiting the video 'canplay' event. */
+    tryPlayVideoTimeout?: number;
+}