Examine source code of Youtube Checkmaker

{
  "manifest_version": 2,
  "name": "Youtube Checkmaker",
  "version": "1.0",
  "description": "Save youtube videos with timestamp as bookmark",
  "permissions": [
    "contextMenus",
    "tabs",
    "bookmarks"
  ],
  "background": {
    "persistent": false,
    "scripts": [
      "js/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "js/content.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "images/icon.png",
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "images/icon.png",
    "32": "images/icon.png",
    "48": "images/icon.png",
    "128": "images/icon.png"
  }
}