Page Ruler

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Page Ruler",
  "version": "1.0",
  "description": "Use the Page Ruler to measure the web for width, height of any section of your choice",
  "permissions": [
    "activeTab",
    "scripting"
  ],
  "action": {
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "background": {
    "service_worker": "background.js"
  }
}