Examine source code of Furigana Maker

{
  "manifest_version": 3,
  "name": "Furigana Maker",
  "description": "__MSG_extDescription__",
  "version": "3.8.1",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "128": "icons/128.png"
  },
  "permissions": [
    "contextMenus",
    "storage"
  ],
  "default_locale": "en",
  "homepage_url": "https://furiganamaker.app",
  "commands": {
    "addFurigana": {
      "description": "__MSG_shortcutAddFurigana__"
    },
    "toggleAutoMode": {
      "description": "__MSG_shortcutToggleAutoMode__"
    },
    "toggleKanjiFilter": {
      "description": "__MSG_shortcutToggleKanjiFilter__"
    },
    "toggleFuriganaVisibility": {
      "description": "__MSG_shortcutToggleFuriganaVisibility__"
    },
    "openPlaygroundPage": {
      "description": "__MSG_shortcutOpenPlayground__"
    },
    "openOptionsPage": {
      "description": "__MSG_shortcutOpenOptions__"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f610e21f-3434-46e8-8db2-a811f4dbfd5f}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "type": "module",
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_title": "Popup | Furigana Maker",
    "default_popup": "popup.html"
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/autoMark.js"
      ]
    },
    {
      "matches": [
        "*://*/*"
      ],
      "run_at": "document_start",
      "js": [
        "content-scripts/handleEvent.js"
      ]
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "content-scripts/autoMark.css"
      ],
      "use_dynamic_url": true,
      "matches": [
        "*://*/*"
      ]
    }
  ],
  "content_security_policy": {
    "extension_pages": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'"
  }
}