Examine source code of Anti-Flashbang

{
  "manifest_version": 2,
  "name": "Anti-Flashbang",
  "version": "1.2.1",
  "description": "Dark background only. No per-element inversion, no broken pages.",
  "permissions": [
    "storage",
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "curtain.css"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Anti-Flashbang"
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "anti-flashbang@local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}