Examine source code of EmailHook

{
  "manifest_version": 3,
  "name": "EmailHook",
  "description": "Extract emails from Gmail contacts & websites. Select emails, save locally in Firefox, export anytime. Auto-fill 'To' field when composing - no tracking, fully private. By EmailnPhoneList.com",
  "author": "EmailnPhoneList.com",
  "version": "1.0.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "david@emailnphonelist.com",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "permissions": [
    "storage",
    "scripting",
    "activeTab"
  ],
  "optional_permissions": [
    "clipboardWrite"
  ],
  "host_permissions": [
    "https://mail.google.com/*",
    "https://gmail.com/*"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_title": "EmailHook - Find Emails Fast",
    "default_icon": {
      "16": "icons/hook_16x16.png",
      "48": "icons/hook_48x48.png",
      "128": "icons/hook_128x128.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_page": "options.html",
  "icons": {
    "16": "icons/hook_16x16.png",
    "48": "icons/hook_48x48.png",
    "128": "icons/hook_128x128.png",
    "256": "icons/hook_256x256.png"
  },
  "web_accessible_resources": [
    {
      "resources": [
        "styles/*.css",
        "icons/*"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ]
}