Specify when should InputPicker display "Create option" action

[SevenOutman]

What problem does this feature solve?

Most of the time when we use a creatable InputPicker, we don't want user to create a new option with duplicated name with existing entries.

For now InputPicker hides "Create option" action when the search keyword matches any entry's [valueKey], which is not ideal IMO. Instead we tend to avoid duplicated [labelKey] most of the time.

rsuite/src/InputPicker/InputPicker.tsx

Lines 671 to 673 in fafef7c

	if (creatable && searchKeyword && !items.find(item => item[valueKey] === searchKeyword)) {
	items = [...items, createOption(searchKeyword)];
	}

What does the proposed API look like?

Provide a new prop for users to specify whether to display "Create option" action with given keyword. Something like:

type InputPickerProps = {
  shouldDisplayCreateOption?: (keyword: string, data: T[]) => boolean;
}

Usage example:

<InputPicker
  shouldDisplayCreateOption={(keyword, data) => {
    return data.every(item => item.name !== keyword)
  }}
/>