Examine source code of Element Background Setter

{
  "manifest_version": 2,
  "name": "Element Background Setter",
  "version": "1.0",
  "description": "Sets the background of a user-specified element to a user-specified color.",
  "permissions": [
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "element-background-setter@example.com"
    }
  }
}