ToolBarDropdownOptions

A dropdown option switch that chooses between different options and then triggers a callback based on the selected option.

It should be built on top of [ToolBarItem](https://github.com/suda/tool-bar/blob/master/lib/items/tool-bar-item.js).

References: https://guide.freecodecamp.org/javascript/tutorials/how-to-create-a-dropdown-menu-with-css-and-javascript/

Start with lib/items/tool-bar-item.js and review the linked dropdown-menu reference. Define the dropdown option behavior around the existing ToolBarItem, including how selections trigger their callback. Done means the toolbar exposes a working option switch that selects among the provided options and invokes the matching callback.

Written by the indexing model from the issue text.