Examine source code of Readup

{
  "manifest_version": 3,
  "name": "Readup",
  "description": "The best way to read online.",
  "author": "reallyread.it, inc.",
  "icons": {
    "16": "./icons/icon-16.png",
    "24": "./icons/icon-24.png",
    "32": "./icons/icon-32.png",
    "40": "./icons/icon-40.png",
    "48": "./icons/icon-48.png",
    "64": "./icons/icon-64.png",
    "72": "./icons/icon-72.png",
    "96": "./icons/icon-96.png",
    "128": "./icons/icon-128.png"
  },
  "action": {
    "default_icon": {
      "16": "./icons/icon-16.png",
      "24": "./icons/icon-24.png",
      "32": "./icons/icon-32.png",
      "40": "./icons/icon-40.png",
      "48": "./icons/icon-48.png"
    },
    "default_title": "Readup"
  },
  "content_scripts": [
    {
      "matches": [
        "https://readup.org/*"
      ],
      "js": [
        "./content-scripts/web-app/bundle.js"
      ]
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "content-scripts/alert/bundle.css",
        "content-scripts/reader/bundle.css",
        "content-scripts/reader/reset.css",
        "content-scripts/ui/fonts/cambria-bold.ttf",
        "content-scripts/ui/fonts/cambria-regular.ttf",
        "content-scripts/ui/fonts/museo-sans-100.ttf",
        "content-scripts/ui/fonts/museo-sans-300.ttf",
        "content-scripts/ui/fonts/museo-sans-500.ttf",
        "content-scripts/ui/fonts/museo-sans-700.ttf",
        "content-scripts/ui/fonts/museo-sans-900.ttf",
        "content-scripts/ui/images/logo.svg",
        "content-scripts/ui/images/logo-white.svg",
        "options-page/bundle.css"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ]
    }
  ],
  "options_ui": {
    "page": "options-page/index.html",
    "open_in_tab": true
  },
  "permissions": [
    "cookies",
    "scripting",
    "storage",
    "declarativeNetRequest"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "declarative_net_request": {
    "rule_resources": [
      {
        "id": "ruleset",
        "enabled": true,
        "path": "rules.json"
      }
    ]
  },
  "version": "8.1.0",
  "background": {
    "scripts": [
      "./event-page/bundle.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{20f866de-c377-49f8-be05-4c16fb5afdb9}"
    }
  }
}