country selection not mandatory

Hi !
thanks for this component !!
is there a way to make country selection not mandatory, i mean allow selecting an empty value ?

The issue names no file, test, or entry point. Start by locating the country-selection API and determine how an empty selection should be represented; done means optional country selection works without breaking existing selection or validation behavior and is covered by a test.

索引モデルが issue の本文から書いたものです。