Examine source code of Always underline links

{
  "manifest_version": 2,
  "name": "Always underline links",
  "description": "This addon forces links to always be underlined.",
  "version": "1.0.0",
  "icons": {
    "128": "images/icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "css": [
        "main.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "always-underline-links@amo-menkuri.com",
      "strict_max_version": "120.*"
    }
  }
}