extensions/html-language-features/client/src/languageParticipants.ts/isEqualSet
function isEqualSet<T>(s1: Set<T>, s2: Set<T>) {
	if (s1.size !== s2.size) {
		return false;
	}
	for (const e of s1) {
		if (!s2.has(e)) {
			return false;
		}
	}
	return true;
}