This improves use when creating reusable components on top of the input.

• Adds undefined to the country variable type
• Removes newly dead code

Why?

In use cases when you are creating a reusable component that consumes TelInput you will create type errors by making your country prop optional.

export type Props = {
    // Component API calls for an optional country
    country?: CountryCode | null;
    // -- snip --
}

This will have a type error saying type CountryCode | null is not assignable to CountryCode | null | undefined

<TelInput
    bind:country
/>

Using npm link this PR removes the type error from my component.