remove the obsolete jsQr implementation

-@JS()
-library jsqr;
-
-import 'dart:async';
-import 'dart:html';
-import 'dart:typed_data';
-
-import 'package:js/js.dart';
-import 'package:mobile_scanner/src/enums/barcode_format.dart';
-import 'package:mobile_scanner/src/enums/camera_facing.dart';
-import 'package:mobile_scanner/src/objects/barcode.dart';
-import 'package:mobile_scanner/src/web/base.dart';
-
-@JS('jsQR')
-external Code? jsQR(dynamic data, int? width, int? height);
-
-@JS()
-class Code {
-  external String get data;
-
-  external Uint8ClampedList get binaryData;
-}
-
-/// Barcode reader that uses jsQR library.
-/// jsQR supports only QR codes format.
-class JsQrCodeReader extends WebBarcodeReaderBase
-    with InternalStreamCreation, InternalTorchDetection {
-  JsQrCodeReader({required super.videoContainer});
-
-  @override
-  bool get isStarted => localMediaStream != null;
-
-  @override
-  Future<void> start({
-    required CameraFacing cameraFacing,
-    List<BarcodeFormat>? formats,
-    Duration? detectionTimeout,
-  }) async {
-    videoContainer.children = [video];
-
-    if (detectionTimeout != null) {
-      frameInterval = detectionTimeout;
-    }
-
-    final stream = await initMediaStream(cameraFacing);
-
-    prepareVideoElement(video);
-    if (stream != null) {
-      await attachStreamToVideo(stream, video);
-    }
-  }
-
-  @override
-  void prepareVideoElement(VideoElement videoSource) {
-    // required to tell iOS safari we don't want fullscreen
-    videoSource.setAttribute('playsinline', 'true');
-  }
-
-  @override
-  Future<void> attachStreamToVideo(
-    MediaStream stream,
-    VideoElement videoSource,
-  ) async {
-    localMediaStream = stream;
-    videoSource.srcObject = stream;
-    await videoSource.play();
-  }
-
-  @override
-  Stream<Barcode?> detectBarcodeContinuously() async* {
-    yield* Stream.periodic(frameInterval, (_) {
-      return _captureFrame(video);
-    }).asyncMap((event) async {
-      final code = await event;
-      if (code == null) {
-        return null;
-      }
-      return Barcode(
-        rawValue: code.data,
-        rawBytes: Uint8List.fromList(code.binaryData),
-        format: BarcodeFormat.qrCode,
-      );
-    });
-  }
-
-  @override
-  Future<void> stopDetectBarcodeContinuously() async {
-    return;
-  }
-
-  /// Captures a frame and analyzes it for QR codes
-  Future<Code?> _captureFrame(VideoElement video) async {
-    if (localMediaStream == null) return null;
-    final canvas =
-        CanvasElement(width: video.videoWidth, height: video.videoHeight);
-    final ctx = canvas.context2D;
-
-    ctx.drawImage(video, 0, 0);
-    final imgData = ctx.getImageData(0, 0, canvas.width!, canvas.height!);
-
-    final code = jsQR(imgData.data, canvas.width, canvas.height);
-    return code;
-  }
-}