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

node_modules/@zxing/text-encoding/esm/coders/utf-8/UTF8Encoder.d.ts

@@ -0,0 +1,18 @@
+import { Stream } from "../../common/Stream";
+/**
+ * @constructor
+ * @implements {Encoder}
+ * @param {{fatal: boolean}} options
+ */
+export declare class UTF8Encoder {
+    readonly fatal: boolean;
+    constructor(options: {
+        fatal: boolean;
+    });
+    /**
+     * @param {Stream} stream Input stream.
+     * @param {number} code_point Next code point read from the stream.
+     * @return {(number|!Array.<number>)} Byte(s) to emit.
+     */
+    handler(stream: Stream, code_point: number): (number | Array<number>);
+}