Examine source code of White to Black

{
  "manifest_version": 2,
  "name": "WhiteToBlack",
  "version": "1.1.1",
  "description": "Switch between light and dark themes with customizable hue.",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "clipboardWrite",
    "storage",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "64": "icons/icon64.png",
      "128": "icons/icon128.png",
      "256": "icons/icon256.png",
      "512": "icons/icon512.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{bcfe89e0-df4f-4a12-8e79-5a45a2c712cd}"
    }
  }
}