Examine source code of UnTab

{
  "manifest_version": 2,
  "name": "UnTab",
  "version": "0.4.0",
  "author": "Akash Hamirwasia",
  "description": "Search through tabs, history, bookmarks and perform common browser actions like a hero!",
  "homepage_url": "https://getuntab.now.sh",
  "icons": {
    "48": "static/icons/icon_48.png",
    "96": "static/icons/icon_96.png",
    "128": "static/icons/icon_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content/content.js"
      ],
      "css": [
        "content/styles.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "index.html"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {},
  "commands": {
    "toggle-search": {
      "suggested_key": {
        "default": "Ctrl+Shift+Space",
        "mac": "Command+Shift+Space"
      },
      "description": "Send a 'toggle-search' event to the extension"
    }
  },
  "permissions": [
    "tabs",
    "history",
    "bookmarks",
    "storage",
    "https://api.duckduckgo.com/*"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'; img-src http: https: data:"
}