normalize method
Implementation
double normalize(double end, [double start = 0, int roundTo = 6]) {
final tuple = start.sort(end);
start = tuple.first.toDouble();
end = tuple.second.toDouble();
if (this <= start) return 0;
if (this >= end) return 1;
final div = (this - start) / (end - start);
return div.roundTo(roundTo);
}