Examine source code of Save As eBook

{
  "manifest_version": 2,
  "name": "__MSG_extName__",
  "version": "1.4.2",
  "default_locale": "en",
  "author": "Alex Adam",
  "homepage_url": "https://github.com/alexadam/save-as-ebook",
  "description": "Save a web page or selection as eBook (.epub)",
  "icons": {
    "48": "icons/book48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "./libs/jquery.js",
        "./libs/jszip.js",
        "./libs/jszip-utils.js",
        "./libs/pure-parser.js",
        "./libs/cssjson.js",
        "./libs/filesaver.js",
        "saveEbook.js",
        "extractHtml.js",
        "utils.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/book32.png",
    "default_title": "Save as eBook",
    "default_popup": "menu.html"
  },
  "permissions": [
    "contextMenus",
    "activeTab",
    "storage",
    "unlimitedStorage",
    "notifications",
    "<all_urls>"
  ],
  "commands": {
    "save-page": {
      "suggested_key": {
        "default": "Alt+Shift+1"
      },
      "description": "Save current page as eBook"
    },
    "save-selection": {
      "suggested_key": {
        "default": "Alt+Shift+2"
      },
      "description": "Save current selection as eBook"
    },
    "add-page": {
      "suggested_key": {
        "default": "Alt+Shift+3"
      },
      "description": "Add current page as chapter"
    },
    "add-selection": {
      "suggested_key": {
        "default": "Alt+Shift+4"
      },
      "description": "Add current selection as chapter"
    }
  }
}