Replace videoWidth, videoHeight with VideoResizer interface

[dan3988]

I'm using this library and wanted to set a maximum resolution for videos however that is currently not possible. When overriding the default resize function by adding videoWidth and videoHeight to the configuration, this resizes the video to those dimensions exactly. In my case this means that the video is stretched to a 1:1 aspect ratio, and lower resolution videos are upscaled.

I've added a functional interface VideoResizer that allows a custom function to calculate the desired dimension using the source video's dimensions, with some default implementations:

• VideoResizer.auto - Matches the original behavior when not providing videoWidth and videoHeight in the configuration
• VideoResizer.scale - Scale the dimensions by a scale factor
• VideoResizer.limitSize - Set a maximum width and height value for the video
• VideoResizer.matchSize - Set an exact width and height value

I've updated the Configuration class and replaced keepOriginalResolution, videoWidth and videoHeight with resizer, and added a constructor overload to match the old behaviour.