Examine source code of Headline Studio

{
  "manifest_version": 2,
  "name": "Headline Studio by CoSchedule",
  "version": "3.1.7",
  "icons": {
    "16": "assets/icons/favicon-16.png",
    "32": "assets/icons/favicon-32.png",
    "48": "assets/icons/favicon-48.png",
    "64": "assets/icons/favicon-64.png",
    "128": "assets/icons/favicon-128.png",
    "256": "assets/icons/favicon-256.png",
    "512": "assets/icons/favicon-512.png",
    "1024": "assets/icons/favicon-1024.png"
  },
  "description": "The headline analyzer from CoSchedule enables you to create headlines that drives maximum traffic, clicks, & SEO",
  "homepage_url": "https://headlines.coschedule.com",
  "short_name": "Headline Studio",
  "permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "author": "CoSchedule",
  "applications": {
    "gecko": {
      "id": "dev@coschedule.com"
    }
  },
  "browser_action": {
    "default_icon": {
      "16": "assets/icons/favicon-16.png",
      "32": "assets/icons/favicon-32.png",
      "48": "assets/icons/favicon-48.png",
      "64": "assets/icons/favicon-64.png",
      "128": "assets/icons/favicon-128.png",
      "256": "assets/icons/favicon-256.png",
      "512": "assets/icons/favicon-512.png",
      "1024": "assets/icons/favicon-1024.png"
    },
    "default_title": "Headline Studio",
    "browser_style": false
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "background": {
    "scripts": [
      "js/background.bundle.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "js/hub.bundle.js"
      ],
      "css": [
        "css/extension.css"
      ],
      "run_at": "document_idle"
    },
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "js/spoke.bundle.js"
      ],
      "css": [
        "css/extension.css"
      ],
      "run_at": "document_idle",
      "all_frames": true
    }
  ]
}