Examine source code of Short Link Expander

{
  "manifest_version": 2,
  "name": "Short Link Expander",
  "version": "1.0",
  "description": "Expands shortened links on hover and shows their final destination.",
  "permissions": [
    "tabs",
    "webRequest",
    "<all_urls>"
  ],
  "icons": {
    "64": "icon64.png",
    "96": "icon96.png",
    "128": "icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{34d54d85-f723-4b46-847b-0421b896023b}",
      "strict_min_version": "78.0"
    }
  }
}