Add script for download materials and unzip it

[patou]

For reduce the custom script in repository, its can be a good idea to have a script for download materials with config event and not write a custom script for it :

{
  "script": "download-material.sh",
  "env": {
    "google-drive-id": "xxxxx",
    "dest-dir": "/home/ubuntu/corrections",
    "compress": "zip",
  }
},
{
  "script": "download-material.sh",
  "env": {
    "google-drive-id": "yyyyyy",
    "dest-dir": "/home/ubuntu/exercices",
    "compress": "tar.gz",
  }
},
{
  "script": "download-material.sh",
  "env": {
    "google-drive-id": "zzzzz",
    "dest-file": "/home/ubuntu/slides.pdf",
  }
},

[patou]

I see the PR with a proposition like this #19