Examine source code of Readable Wikipedia

{
  "manifest_version": 2,
  "name": "Readable Wikipedia",
  "version": "1.0.1",
  "description": "Truncates the line width of wikipedia articles to make them readable on large screens",
  "icons": {
    "48": "icons/readable-wikipedia-48.png"
  },
  "permissions": [
    "tabs",
    "storage",
    "https://*.wikipedia.org/*"
  ],
  "browser_action": {
    "default_icon": "icons/readable-wikipedia-48.png",
    "default_title": "Readable Wikipedia",
    "default_popup": "popup/popup.html"
  }
}