Seek time and encoder filter

[BDT-4248]

Hi! I was simply thinking that it'd be nice if this package had audio filters and beginning time applied (thus custom ffmpeg support).
Take this for example (taken from another package i use but it's for youtube):

{
    quality: "highestaudio",
    highWaterMark: 1 << 25,
    liveBuffer: 40000,
    opusEncoded: true,
    seek: 0, // where the audio should start (in seconds).. will be defaulted to zero if argument is omitted, seek number is negative or surpasses the total audio duration
    encoderArgs: ['-af', ...], // the "..." is where the filters are applied, like having 8D audio, sped up/slowed down audio, pitched up/down audio, etc.. this omitted will simply be an "unedited" audio - having multiple "filters" are separated by a comma (,)
    dlChunkSize: 0, 
    bitrate: 320
}

Examples:

{
    ...
    seek: 35, // audio would start at 35 seconds
    encoderArgs: ['-af', 'apulsator=hz=0.08'], // having 8D audio
    ...
}

{
    ...
    seek: -1, // audio would start at -1 seconds but will be defaulted to 0
    encoderArgs: ['-af', 'apulsator=hz=0.08,atempo=1.5'], // having 8D audio playing in x1.5 speed
    ...
}

Sorry but explaining in detail is difficult for me so i apologize in case there are any confusions or misunderstandings