Function externalSort

externalSort(
    inputs: string[],
    output: string,
    maxHeap?: number,
    threadCount?: number,
    tmpDir?: string,
): Promise<void>
Sorts an array using external-sorting.
Parameters
- inputs: string[]
  a list of input files without their extensions. e.g. './file1', './file2', './file3'
- output: string
  output folder to place the sorted keys
- maxHeap: number = 100_000
  max instance of the parsed entity in memory
- threadCount: number = 1
  number of workers
- tmpDir: string = ...
  temporary directory
Returns Promise<void>