src/vs/base/common/comparers.ts/compareFileExtensionsUnicode
export function compareFileExtensionsUnicode(one: string | null, other: string | null) {
	one = one || '';
	other = other || '';
	const oneExtension = extractExtension(one).toLowerCase();
	const otherExtension = extractExtension(other).toLowerCase();

	// Check for extension differences
	if (oneExtension !== otherExtension) {
		return oneExtension < otherExtension ? -1 : 1;
	}

	// Check for full filename differences.
	if (one !== other) {
		return one < other ? -1 : 1;
	}

	return 0;
}