feat: provide tree API

[antongolub]

tree()

Returns a child processes list by the specified parent pid. Some kind of shortcut for lookup({ppid: pid}).

import { tree } from '@webpod/ps'

const children = await tree(123) 
/**
[
  {pid: 124, ppid: 123},
  {pid: 125, ppid: 123}
] 
*/

To obtain all nested children, set recursive option to true:

const children = await tree({pid: 123, recursive: true}) 
/**
[
  {pid: 124, ppid: 123},
  {pid: 125, ppid: 123},

  {pid: 126, ppid: 124},
  {pid: 127, ppid: 124},
  {pid: 128, ppid: 124},
  
  {pid: 129, ppid: 125},
  {pid: 130, ppid: 125},
] 
*/