Examine source code of FocusMe

{
  "manifest_version": 3,
  "name": "FocusMe",
  "version": "4.9",
  "description": "Connector to the FocusMe desktop application to track and block websites. Visit https://focusme.com to get the app.",
  "icons": {
    "48": "icons/FocusMe-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "wbproxy@focusme.com",
      "strict_min_version": "109.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup.html",
    "default_title": "FocusMe Status",
    "default_icon": {
      "16": "icons/FocusMe-16.png",
      "32": "icons/FocusMe-32.png",
      "48": "icons/FocusMe-48.png"
    }
  },
  "permissions": [
    "nativeMessaging",
    "tabs",
    "storage"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*",
        "*://*.facebook.com/*"
      ],
      "css": [
        "content.css"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ]
}