Examine source code of web-tree

{
  "manifest_version": 2,
  "name": "web-tree",
  "version": "1.1",
  "description": "Constructs hierarchical tree of URLs as you browse",
  "homepage_url": "https://github.com/zbo14/web-tree",
  "permissions": [
    "webRequest",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "dist/bundle.js",
      "background.js"
    ]
  },
  "devtools_page": "devtools/page.html"
}