v0.4.1

• For -e libvpx-vp9 map --preset number to ffmpeg -cpu-used (0-5).
• When overriding with a ffmpeg encoder avoid setting b:a, movflags or ac if explicitly set via --enc.
• Add error output when using --enc-input with the default svt-av1 encoder.
• Add errors for --enc/--enc-input args that are already provided by existing args or inferred.