Examine source code of Flash Guard

{
  "manifest_version": 2,
  "name": "Flash Guard",
  "version": "1.0.16",
  "description": "Prevents white background flashes during page loads by applying a dark background before content renders.",
  "author": "Flash Guard",
  "homepage_url": "https://github.com/mathieux51/flash-guard-firefox",
  "browser_specific_settings": {
    "gecko": {
      "id": "flash-guard@mathieux51.dev",
      "strict_min_version": "95.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "browserSettings",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "src/background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "src/content.js"
      ],
      "css": [
        "src/flash-guard.css"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_title": "Flash Guard",
    "default_popup": "src/popup.html"
  },
  "options_ui": {
    "page": "src/options.html",
    "browser_style": true
  }
}