Examine source code of 連番ダウンローダー: Download numbered images

{
  "manifest_version": 2,
  "name": "連番ダウンローダー: Download numbered images",
  "version": "1.2.2",
  "description": "An extension that downloads a batch of images from a website and numbers them consecutively.",
  "homepage_url": "https://github.com/OkanoShinri/Download-Numbered-Images",
  "icons": {
    "48": "icons/48.png",
    "96": "icons/96.png"
  },
  "permissions": [
    "<all_urls>",
    "tabs",
    "activeTab",
    "downloads",
    "storage",
    "notifications",
    "menus"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "src/content_scripts/send_selection.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/32.png",
    "default_title": "連番ダウンローダー: Download numbered images",
    "default_popup": "src/popup/popup.html"
  },
  "options_ui": {
    "page": "src/option/options.html"
  },
  "background": {
    "scripts": [
      "src/background-scripts/background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{0d393fd5-4d1b-4be5-bf34-ef7555e8cd5f}"
    }
  }
}