feat: Add lifecycle hooks

[jingyuexing]

like this:

import { 
      downloadFailed,
      downloadAborted,
      downloadCompleted,
      connectFailed
} from 'maria2'

downloadFailed((e)=>{
console.log(e.reason,e.filename,e.filesize,e.progress)
})

[hydrati]

See https://aria2.github.io/manual/en/html/aria2c.html#notifications

This library is just a simple low-level client implementation.

[yjl9903]

I want to build a high-level abstract of aria2 based on this.

Maybe you can help :)

I think there should be a class Aria2Client with a download method, like the following prototype:

download(<magnet/torrent file/...>,
  options: { ..., callbacks: { progress(percent) {}, ... } }): Promise<{ status: 'ok' | 'aborted' | 'failed' | ..., ... }>

By the way, I have tried implementing this here

[jingyuexing]

impl #8