Examine source code of Readable

{
  "manifest_version": 2,
  "name": "Readable",
  "version": "1.5.0",
  "description": "Converts custom font characters to standard alphabetic characters.",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "readable.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "readable_background.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "webRequest",
    "tabs"
  ]
}