Examine source code of Distracted Reader

{
  "name": "Distracted Reader",
  "description": "Select any text, learn something new.",
  "version": "1.5.2",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "background/background.js"
    ],
    "persistent": true
  },
  "browser_action": {},
  "commands": {
    "toggle-extension": {
      "suggested_key": {
        "default": "Alt+D",
        "mac": "Alt+D"
      },
      "description": "Enable/disable extension"
    }
  },
  "permissions": [
    "tabs",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "icons": {
    "16": "icons/app16.png",
    "48": "icons/app48.png",
    "128": "icons/app128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "all_frames": true,
      "js": [
        "content/content.js"
      ]
    },
    {
      "matches": [
        "https://*.m.wikipedia.org/*",
        "https://*.m.wiktionary.org/*"
      ],
      "all_frames": true,
      "css": [
        "wiki.css"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "content/content.css"
  ]
}