Examine source code of Night Mode v1

{
  "manifest_version": 2,
  "name": "Night Mode",
  "version": "1.0",
  "description": "Dark theme for webpages",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Night Mode"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7d9ae2f8-caa5-45ee-8ce3-c88b0d4df536}"
    }
  }
}