• Add --encoder/-e encoder override.
  Any encoder ffmpeg supports
  and that may be controlled using -crf may be used.
• Add --enc $FFMPEG_ARG for providing arbitrary output options to the ffmpeg encoder invocation.
  These only work when overriding the encoder with -e.
  
  E.g. Set x265 params: -e libx265 --enc x265-params=lossless=1.
• Add --enc-input $FFMPEG_ARG for providing ffmpeg input file options, similar to --enc.
• --preset now supports also word presets like slow, veryfast for ffmpeg encoders like libx264.
• --preset is no longer required. Default svt-av1 --preset is now 8.
• Support setting keyint for -e encoders in a similar way as is done for av1.
• Add default vp9 & libaom-av1 -b:v 0 setting so constant quality crf based encoding works consistently.
• For -e libaom-av1 map --preset number to ffmpeg -cpu-used (0-8).
• For *_vaapi encoders map --crf to ffmpeg -qp as crf is not supported.
• Shell escape file name in "Encoding ..." output.