Examine source code of Short URL Expand

{
  "manifest_version": 2,
  "name": "Short URL Expander",
  "version": "1.0",
  "description": "Expand shortened URLs on hover",
  "icons": {
    "64": "icon64.png",
    "128": "icon128.png"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{450f51a4-c0de-4fd3-97c6-961c8c80f089}",
      "strict_min_version": "120.0"
    }
  }
}