[feature request] keep the same width and height, and reduce the quality only

[GeekaholicLin]

Thanks for the awesome library for the image compression!

I noticed that the width/height of the image will be reduced to meet the maxSizeMB.

Is it possible to provide the option to keep the same width and height of the original image file and reduce the quality only?

https://github.com/Donaldcwl/browser-image-compression/blob/master/lib/image-compression.js#L95-L96

[Donaldcwl]

v2.0.0 added options.alwaysKeepResolution, for example:

const options = {
    maxSizeMB: 1,
    useWebWorker: true,
    alwaysKeepResolution: true,
  }
  const compressedFile = await imageCompression(imageFile, options);