Examine source code of Readhook Reading

{
  "manifest_version": 2,
  "name": "Readhook",
  "version": "2.6",
  "description": "Thickens 40-55% of the text and makes it easier to read",
  "browser_action": {
    "default_title": "ReadHook",
    "default_popup": "assets/index.html"
  },
  "permissions": [
    "activeTab",
    "<all_urls>",
    "tabs"
  ],
  "icons": {
    "128": "assets/icon/icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "martinwolski04@gmail.com"
    }
  }
}