Examine source code of trellozen

{
  "manifest_version": 2,
  "name": "trellozen",
  "author": "Thomas Reese",
  "version": "2.0.1",
  "description": "Allows you to also set a custom background to each individual Trello Board using any available image URL from the web.",
  "icons": {
    "48": "icons/trellozen-48.png",
    "96": "icons/trellozen-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.trello.com/b/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "page_action": {
    "browser_style": true,
    "default_icon": "icons/trellozen-32.png",
    "default_title": "Change this Trello boards background.",
    "default_popup": "popup/page-action-popup.html",
    "show_matches": [
      "https://*.trello.com/b/*"
    ]
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "https://*.trello.com/b/*",
    "activeTab",
    "tabs",
    "storage"
  ]
}