Examine source code of Scrummer

{
  "name": "Scrummer",
  "version": "0.26resigned1",
  "description": "Adds Storypoints to Trello",
  "content_scripts": [
    {
      "run_at": "document_end",
      "matches": [
        "https://trello.com/*"
      ],
      "js": [
        "scrummer.js"
      ],
      "css": [
        "scrummer.css"
      ]
    }
  ],
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "scrummer@jetpack"
    }
  },
  "icons": {
    "48": "img/icon48.png",
    "128": "img/icon128.png",
    "1024": "img/icon1024.png"
  }
}