This adds analysis options and also removes several warnings that come along with flutter v3.

Here's an example of a warning on current stable flutter:

../../_tool/flutter/.pub-cache/hosted/pub.dartlang.org/flutter_gif-0.0.4/lib/flutter_gif.dart:235:42: Warning: Operand of null-aware operation '!' has type 'PaintingBinding' which excludes null.
 - 'PaintingBinding' is from 'package:flutter/src/painting/binding.dart' ('../../_tool/flutter/packages/flutter/lib/src/painting/binding.dart').
  ui.Codec codec = await PaintingBinding.instance!

I noticed that if the current frame contains the same image info, they are only considered as one frame which makes the actual gif unable to play the complete gif frame/duration.

To make things clear, here's an example gif:

The first( image with #1) frame's duration is 4 seconds but when played, it only shows 1 frame since they're all the same. Then the rest is fine since they're all playing at 1 sec, meaning 1 frame.

So to fix that, I added a validator that loop and checks whether the actual duration/frame was added to the list of ImageInfos.

    for (int sec = 1; sec <= duration; sec++) {
      infos.add(ImageInfo(image: frameInfo.image));
    }

Another thing, I replaced this deprecated method:

ui.Codec codec = await PaintingBinding.instance.instantiateImageCodec(bytes);

'instantiateImageCodec' is deprecated and shouldn't be used. Use instantiateImageCodecFromBuffer with an ImmutableBuffer instance instead. This feature was deprecated after v2.13.0-1.0.pre..

by using the suggested:

  final buffer = await ImmutableBuffer.fromUint8List(bytes);
  ui.Codec codec =
      await PaintingBinding.instance.instantiateImageCodecFromBuffer(buffer);