Examine source code of cfsnow

{
  "manifest_version": 2,
  "name": "cfsnow",
  "version": "1.1resigned1",
  "description": "remove snow background from cf",
  "icons": {
    "48": "favicon.png"
  },
  "applications": {
    "gecko": {
      "id": "cfsnow@gir.org",
      "strict_min_version": "45.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.codeforces.com/*"
      ],
      "js": [
        "scr.js"
      ]
    }
  ]
}