Examine source code of Send to Outline

{
  "manifest_version": 2,
  "name": "Send to Outline",
  "version": "1.4.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "{d527189b-f581-4bc5-b974-cd161115459a}",
      "strict_min_version": "67.0"
    }
  },
  "description": "Sends the reader to the same article on https://outline.com",
  "icons": {
    "48": "icons/md-arrow-round-forward.svg",
    "96": "icons/md-arrow-round-forward.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/page-16.png",
      "32": "icons/page-32.png"
    }
  },
  "permissions": [
    "tabs",
    "contextMenus"
  ]
}