Add loading screen, login persistence

Avalonia.Labs.Gif/Avalonia.Labs.Gif.csproj

Avalonia.Labs.Gif/Decoding/BlockTypes.cs

Avalonia.Labs.Gif/Decoding/ExtensionType.cs

Avalonia.Labs.Gif/Decoding/FrameDisposal.cs

Avalonia.Labs.Gif/Decoding/GifColor.cs

Avalonia.Labs.Gif/Decoding/GifDecoder.cs

Avalonia.Labs.Gif/Decoding/GifFrame.cs

Avalonia.Labs.Gif/Decoding/GifHeader.cs

Avalonia.Labs.Gif/Decoding/GifRect.cs

Avalonia.Labs.Gif/Decoding/GifRepeatBehavior.cs

Avalonia.Labs.Gif/Decoding/InvalidGifStreamException.cs

Avalonia.Labs.Gif/Decoding/LzwDecompressionException.cs

Avalonia.Labs.Gif/Extensions/StreamExtensions.cs

Avalonia.Labs.Gif/GifCompositionCustomVisualHandler.cs

Avalonia.Labs.Gif/GifDrawPayload.cs

Avalonia.Labs.Gif/GifImage.cs

Avalonia.Labs.Gif/GifInstance.cs

Avalonia.Labs.Gif/HandlerCommand.cs

Blacklight.sln

Blacklight/App.axaml