Examine source code of Yet Another Undo Close Tab

{
  "version": "0.2.5",
  "name": "Yet Another Undo Close Tab",
  "short_name": "YAUCT",
  "description": "Open closed tab with with additional features like quick search",
  "author": "Andrii Volosovych",
  "homepage_url": "https://www.linkedin.com/in/andreyvolosovich/",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{473bf340-8c1d-4cb3-ae2b-909f674c4e6e}"
    }
  },
  "permissions": [
    "tabs",
    "storage",
    "sessions",
    "menus"
  ],
  "options_ui": {
    "open_in_tab": true,
    "page": "pages/options/index.html"
  },
  "background": {
    "scripts": [
      "lib/constants.js",
      "lib/core.js",
      "lib/background.js",
      "lib/contextMenu.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup/index.html",
    "default_title": "Open recently closed tabs",
    "default_icon": {
      "16": "icons/light/16.png",
      "32": "icons/light/32.png",
      "48": "icons/light/48.png",
      "64": "icons/light/64.png",
      "128": "icons/light/128.png",
      "256": "icons/light/256.png"
    },
    "theme_icons": [
      {
        "light": "icons/light/16.png",
        "dark": "icons/dark/16.png",
        "size": 16
      },
      {
        "light": "icons/light/32.png",
        "dark": "icons/dark/32.png",
        "size": 32
      },
      {
        "light": "icons/light/48.png",
        "dark": "icons/dark/48.png",
        "size": 48
      },
      {
        "light": "icons/light/64.png",
        "dark": "icons/dark/64.png",
        "size": 64
      },
      {
        "light": "icons/light/128.png",
        "dark": "icons/dark/128.png",
        "size": 128
      },
      {
        "light": "icons/light/256.png",
        "dark": "icons/dark/256.png",
        "size": 256
      }
    ]
  },
  "icons": {
    "16": "icons/alt/16.png",
    "32": "icons/alt/32.png",
    "48": "icons/alt/48.png",
    "64": "icons/alt/64.png",
    "128": "icons/alt/128.png",
    "256": "icons/alt/256.png"
  }
}