Examine source code of Dark Mode

{
  "manifest_version": 2,
  "name": "Dark Mode",
  "version": "1.11.3",
  "description": "Adds a dark screen over everything",
  "icons": {
    "16": "moon.svg",
    "32": "moon.svg",
    "48": "moon.svg",
    "128": "moon.svg"
  },
  "permissions": [
    "<all_urls>",
    "menus",
    "storage",
    "tabs",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "main.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "gayali1rohit@gmail.com"
    }
  },
  "browser_action": {
    "default_icon": {
      "16": "moon.svg",
      "32": "moon.svg",
      "48": "moon.svg",
      "64": "moon.svg",
      "128": "moon.svg"
    },
    "default_title": "Click to toggle darkmode on/off or middle click to change the settings"
  },
  "options_ui": {
    "open_in_tab": false,
    "page": "options.html"
  },
  "commands": {
    "toggleExclude": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y"
      },
      "description": "Toggle excluding the current site"
    }
  }
}