Examine source code of Video Progress Sync

{
  "manifest_version": 2,
  "name": "Video Progress Sync",
  "version": "1.0",
  "description": "Adds timestamp of a YouTube video on pause to history item to easily resume from history or other devices.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "history",
    "activeTab",
    "tabs",
    "storage",
    "*://*.youtube.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false,
    "type": "module"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "lyleleno@gmail.com",
      "strict_min_version": "42.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "inject.js"
      ]
    }
  ]
}