Examine source code of Toggle Wikipedia Sidebar

{
  "manifest_version": 2,
  "name": "Toggle Wikipedia Sidebar",
  "description": "Allows the user to hide Wikipedia's left sidebar.",
  "version": "1.1",
  "author": "Adapted from Sin Jeong-hun",
  "permissions": [
    "https://*.wikipedia.org/wiki/*",
    "https://*.wikipedia.org/w/*",
    "webRequest",
    "webRequestBlocking",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.wikipedia.org/wiki/*",
        "https://*.wikipedia.org/w/*"
      ],
      "js": [
        "modifier.js"
      ],
      "css": [
        "my.css"
      ]
    }
  ]
}