shouldShow method
Whether the hint should show (see class doc). minVersion — the app
version the hint targets; null — "show once ever".
Implementation
@override
bool shouldShow(String key, {String? minVersion}) {
final last = _shown[key];
if (last == null) return true;
if (minVersion == null) return false;
return compareVersions(last, minVersion) < 0;
}