Examine source code of YoutubeResume

{
  "manifest_version": 3,
  "name": "Resume YouTube Playback",
  "version": "1.0",
  "description": "Automatically saves YouTube video progress and lets you resume playback.",
  "browser_specific_settings": {
    "gecko": {
      "id": "mon-extension@example.com"
    }
  },
  "permissions": [
    "storage",
    "tabs",
    "scripting",
    "activeTab"
  ],
  "host_permissions": [
    "*://www.youtube.com/*"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ]
}