Examine source code of Dark Mode

{
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "all_frames": true,
      "match_about_blank": true,
      "js": [
        "content/inject.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "91.0",
      "id": "{87a76b98-cb15-4705-8f03-f24522ddfcd9}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "name": "Dark Mode",
  "icons": {
    "16": "img/moon_icon.png",
    "32": "img/moon_icon.png",
    "48": "img/moon_icon.png",
    "96": "img/moon_icon.png"
  },
  "description": "Apply a comfortable dark theme to any website with one click. Adjust brightness, contrast, and warmth, whitelist sites, and read lon",
  "background": {
    "persistent": false,
    "scripts": [
      "background/background.js"
    ]
  },
  "version": "1.1.2",
  "manifest_version": 2,
  "browser_action": {
    "default_icon": {
      "16": "img/moon_icon.png",
      "32": "img/moon_icon.png",
      "48": "img/moon_icon.png",
      "96": "img/moon_icon.png"
    },
    "default_popup": "popup/popup.html",
    "default_title": "Dark Mode"
  },
  "permissions": [
    "storage",
    "tabs",
    "<all_urls>",
    "webRequest",
    "webRequestBlocking"
  ]
}