Examine source code of Cover Download

{
  "manifest_version": 2,
  "name": "Cover Download",
  "version": "1.3.2",
  "description": "Generate a download button in the top right corner of a cover image and enable downloading the cover image upon clicking.",
  "permissions": [
    "activeTab",
    "downloads",
    "downloads.open"
  ],
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a3c5f0cb-dea9-4672-bbd9-77eaa9188773}"
    }
  }
}