Examine source code of Reading Mode Pro IM

{
  "manifest_version": 3,
  "name": "Reading Mode Pro",
  "version": "1.0",
  "description": "Enable a distraction-free reading mode with customizable font size and line spacing.",
  "permissions": [
    "activeTab",
    "storage",
    "commands"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "commands": {
    "toggle-reading-mode": {
      "suggested_key": {
        "default": "Ctrl+Shift+R"
      },
      "description": "Toggle reading mode"
    }
  },
  "icons": {
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "reading-mode-pro@myextension.com"
    }
  }
}