Examine source code of EmailAddressPlus

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "version": "1.0",
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "email-address-plus@kud.io"
    }
  },
  "browser_action": {
    "default_title": "__MSG_extensionName__"
  },
  "permissions": [
    "activeTab",
    "storage",
    "clipboardWrite"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options/index.html",
    "browser_style": true
  },
  "icons": {
    "16": "icons/icon.svg",
    "32": "icons/icon.svg",
    "48": "icons/icon.svg"
  }
}