Examine source code of SEOTesting

{
  "manifest_version": 2,
  "name": "SEOTesting",
  "homepage_url": "https://www.seotesting.com/",
  "version": "1.3.9",
  "description": "On-Page SEO, and SEOTesting.com Test Information (Current Page Queries and Test Status)",
  "icons": {
    "16": "assets/icon_16.png",
    "32": "assets/icon_32.png",
    "48": "assets/icon_48.png",
    "128": "assets/icon_128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_page": "options.html",
  "browser_action": {
    "default_popup": "index.html",
    "default_icon": {
      "16": "assets/icon_16.png",
      "32": "assets/icon_32.png",
      "48": "assets/icon_48.png",
      "128": "assets/icon_128.png"
    }
  },
  "permissions": [
    "storage",
    "tabs",
    "https://*/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*/*"
      ],
      "css": [
        "inject.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "assets/icon_16.png",
    "assets/icon_32.png",
    "assets/icon_48.png",
    "assets/icon_128.png",
    "index.html",
    "options.html",
    "inject.css"
  ],
  "optional_permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{df262384-a57e-485e-9673-37bd7b29558a}"
    }
  }
}