Examine source code of Collapsible Trello Lists

{
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "description": "Allows the user to collapse Trello lists. List setting is stored in extension storage.",
  "browser_action": {
    "default_icon": "icon.png"
  },
  "manifest_version": 2,
  "name": "Collapsible Trello Lists",
  "version": "1.1.11",
  "permissions": [
    "tabs",
    "storage",
    "*://trello.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "trello-collapse-columns@webrender.net"
    }
  }
}