Examine source code of Cleanup Gmail

{
  "manifest_version": 3,
  "name": "CleanupGmail",
  "version": "1.0.0",
  "description": "A privacy-focused Firefox extension to bulk-mark thousands of Gmail messages as read.",
  "browser_specific_settings": {
    "gecko": {
      "id": "cleanupgmail@local",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "assets/icon-16.png",
    "48": "assets/icon-48.png",
    "128": "assets/icon-128.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "host_permissions": [
    "https://script.google.com/*",
    "https://script.googleusercontent.com/*",
    "https://mail.google.com/*"
  ],
  "background": {
    "scripts": [
      "scripts/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "js": [
        "scripts/content.js"
      ]
    }
  ],
  "action": {
    "default_popup": "popup/popup.html",
    "default_title": "CleanupGmail"
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  }
}