Examine source code of Fiicen Improver

{
  "manifest_version": 3,
  "name": "Fiicen Improver",
  "version": "1.3.0",
  "description": "Fiicenを使いやすくしてくれる非公式拡張機能",
  "permissions": [
    "storage",
    "declarativeNetRequest",
    "notifications"
  ],
  "icons": {
    "64": "images/icon_64x64.png",
    "96": "images/icon_96x96.png",
    "128": "images/icon_128x128.png"
  },
  "action": {
    "default_title": "Fiicen Improver Settings",
    "default_icon": "images/icon_128x128.png",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://fiicen.jp/*"
      ],
      "run_at": "document_start",
      "js": [
        "js/startup.js"
      ]
    },
    {
      "matches": [
        "https://fiicen.jp/*"
      ],
      "run_at": "document_end",
      "css": [
        "index.css"
      ],
      "js": [
        "js/qrcode.js",
        "js/index.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "web_accessible_resources": [
    {
      "resources": [
        "images/*",
        "js/*",
        "about.html",
        "qr-button.html"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "declarative_net_request": {
    "rule_resources": [
      {
        "id": "ruleset",
        "enabled": true,
        "path": "ruleset.json"
      },
      {
        "id": "datasaver",
        "enabled": false,
        "path": "datasaver.json"
      }
    ]
  },
  "host_permissions": [
    "*://*.fiicen.jp/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "FiicenImprover@RasPython3"
    }
  }
}