Examine source code of Wikipedia Expander

{
  "manifest_version": 2,
  "name": "Wikipedia Expander",
  "version": "1.0.2",
  "author": "PlatinPython",
  "description": "Makes the new Wikipedia UI not limit the content width by default.",
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.wikipedia.org/*",
        "*://*.mediawiki.org/*"
      ],
      "js": [
        "wikipedia_expander.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "wikipedia_expander@platinpython"
    }
  }
}