Effect only works as intended on certain image sizes

[Jesper-Hustad]

Currently the wave distort effect has a hard coded distort amount per pixel.
This works well for simple screenshots of designs.

A common use case is saving pages as high resolution images.
The hardcoded effect will therefore be hardly noticeable in those circumstances.

Solution: make the effect scale depending on resolution

The filter where this code is located is called effectDistortWave in filters.js