Fix: Initialize 'audio_details' and 'video_details' properties and update codecData documentation

[DongSeonYoo]

When uploading a video without audio, the 'data' parameter passed to the callback function in the codecData event is as follows.

const command = Ffmpeg(inputFilePath)
    .setFfmpegPath(ffmpegInstall.path)
    .outputOptions([
   '-profile:v baseline',
   '-level 3.0',
   '-start_number 0',
   '-hls_time 10',
   '-hls_list_size 0',
   '-f hls',
]);

command.on('codecData', (data) => {
   console.log('codecData: ', data);
});

# Output Result

codecData:  {
  format: 'mov,mp4,m4a,3gp,3g2,mj2',
  audio: '',
  video: 'h264 (Constrained Baseline) (avc1 / 0x31637661)',
  duration: '00:00:05.00',
  video_details: [
    'h264 (Constrained Baseline) (avc1 / 0x31637661)',
    'yuv420p',
    '600x336 [SAR 1:1 DAR 25:14]',
    '127 kb/s',
    '10 fps',
    '10 tbr',
    '10240 tbn',
    '20 tbc (default)'
  ]
}

As shown in the example above, the 'audio' property is initialized as an empty string. However, upon examining the original code, we notice an inconsistency: while the 'audio' property is initialized with an empty string, the 'audio_details' property is not initialized at all. This situation presents two issues:

1. Lack of code consistency: The 'audio' property is initialized, but 'audio_details' is not.
2. Lack of code consistency: The 'video' property is initialized, but 'video_details' is not.
3. Discrepancy with @types/fluent-ffmpeg: In the type definitions of @types/fluent-ffmpeg, 'audio_details' is defined as a required string[], not an optional one.

These inconsistencies can lead to confusion among developers and may cause unexpected errors during type checking. Furthermore, it creates a mismatch between the actual implementation and the type definitions, potentially leading to runtime errors that are not caught during development.

Therefore, I have added an initialization statement for audio_details as follows

inputStack[inputIndex] = { format: format[1], audio: '', audio_details: '', video: '', video_details: '', duration: '' };

Add duration property to codecData JSDoc

@param {String} codecData.duration input video duration

Remove unused varibales

var path = require('path');
var fs = require('fs');