Add Resize Option

[tworkool]

Hello,
please add an option for a target size and resizing strategy or just a scaling factor.
For example:
Input image is "in_image.jpg" (500x200) and I would like to convert to webp with dimensions 256x256 where the resizing strategy is "fit".
Or if I just want a relative scale I would pass a scaling factor of 0.5 and the resulting image would have dimensions 250x100.

If I have some more time I can try to implement myself... but I generally think it would be a great feature for web developers :)