Examine source code of Happy Reader

{
  "manifest_version": 3,
  "name": "Happy Reader",
  "version": "1.0.0",
  "description": "Make any page a pleasure to read. Dark backgrounds, beautiful typography, and 30 hand-picked themes — anime included.",
  "permissions": [
    "storage",
    "activeTab",
    "scripting",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content/content.js"
      ],
      "run_at": "document_start",
      "all_frames": false
    }
  ],
  "action": {
    "default_popup": "src/popup/popup.html",
    "default_title": "Happy Reader"
  },
  "commands": {
    "toggle-reader-mode": {
      "suggested_key": {
        "default": "Alt+D"
      },
      "description": "Toggle Happy Reader on this page"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "happy-reader@pppppp.dev",
      "strict_min_version": "113.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}