[Feature Request] AVIsynth script support

[wdstudios2]

You obviously wouldn't want to do a lot of computationally intensive filtering in something that's being livestreamed. However, a lot of downloaded footage only requires computationally cheap adjustments (cropping, trimming, splicing) to make it suitable for our intended use cases. In these cases, performing these operations on-the-fly with AVIsynth makes a lot more sense than re-encoding ahead of time and adding more generational loss.