src/vs/base/common/comparers.ts/compareFileExtensions
export function compareFileExtensions(one: string | null, other: string | null): number {
	const [oneName, oneExtension] = extractNameAndExtension(one);
	const [otherName, otherExtension] = extractNameAndExtension(other);

	let result = intlFileNameCollatorBaseNumeric.value.collator.compare(oneExtension, otherExtension);

	if (result === 0) {
		// Using the numeric option will  make compare(`foo1`, `foo01`) === 0. Disambiguate.
		if (intlFileNameCollatorBaseNumeric.value.collatorIsNumeric && oneExtension !== otherExtension) {
			return oneExtension < otherExtension ? -1 : 1;
		}

		// Extensions are equal, compare filenames
		result = intlFileNameCollatorBaseNumeric.value.collator.compare(oneName, otherName);

		if (intlFileNameCollatorBaseNumeric.value.collatorIsNumeric && result === 0 && oneName !== otherName) {
			return oneName < otherName ? -1 : 1;
		}
	}

	return result;
}