add custom video track settings class for web

+import 'dart:js_interop';
+
+import 'package:web/web.dart';
+
+/// This class defines the settings for a video track.
+///
+/// Since the [MediaTrackSettings] type is the full union of both the base MediaTrackSettings,
+/// the tracks settings for audio tracks, and the tracks settings for video tracks,
+/// this class only keeps track of the video track settings.
+///
+/// See also:
+///  * https://www.w3.org/TR/mediacapture-streams/#media-track-settings
+///  * https://www.w3.org/TR/image-capture/#mediatracksettings-section
+class VideoTrackSettings {
+  /// Creates a [VideoTrackSettings] instance from a [MediaStreamTrack].
+  ///
+  /// Since the actual track settings might not have specify all required properties,
+  /// query the capabilities before using specific settings.
+  ///
+  /// Unsupported values fall back to their defaults.
+  factory VideoTrackSettings(MediaStreamTrack videoTrack) {
+    assert(videoTrack.kind == 'video', 'The given track is not a video track.');
+
+    final MediaTrackSettings settings = videoTrack.getSettings();
+    final MediaTrackCapabilities capabilities = videoTrack.getCapabilities();
+
+    final JSAny? facingModeCapability = capabilities.facingMode as JSAny?;
+    final JSAny? focusDistanceCapability = capabilities.focusDistance as JSAny?;
+    final JSAny? focusModeCapability = capabilities.focusMode as JSAny?;
+    final JSAny? torchCapability = capabilities.torch as JSAny?;
+    final JSAny? zoomCapability = capabilities.zoom as JSAny?;
+
+    // The width and height are always supported.
+    return VideoTrackSettings._(
+      width: settings.width,
+      height: settings.height,
+      facingMode:
+          facingModeCapability.isDefinedAndNotNull ? settings.facingMode : '',
+      focusDistance: focusDistanceCapability.isDefinedAndNotNull
+          ? settings.focusDistance.toDouble()
+          : -1.0,
+      focusMode:
+          focusModeCapability.isDefinedAndNotNull ? settings.focusMode : 'none',
+      torch: torchCapability.isDefinedAndNotNull && settings.torch,
+      zoom: zoomCapability.isDefinedAndNotNull ? settings.zoom.toDouble() : 1.0,
+    );
+  }
+
+  /// The private constructor.
+  const VideoTrackSettings._({
+    required this.facingMode,
+    required this.focusDistance,
+    required this.focusMode,
+    required this.height,
+    required this.torch,
+    required this.width,
+    required this.zoom,
+  });
+
+  final String facingMode;
+  final double focusDistance;
+  final String focusMode;
+  final int height;
+  final bool torch;
+  final int width;
+  final double zoom;
+}