Add HowMuch.ToString()

Author: angularsen

UnitsNet.Tests/CustomQuantities/HowMuch.cs

@@ -49,6 +49,7 @@ public IQuantity ToUnit(Enum unit)
 
         public IQuantity ToUnit(UnitSystem unitSystem) => throw new NotImplementedException();
 
+        public override string ToString() => $"{Value} {Unit}";
         public string ToString(string format, IFormatProvider formatProvider) => $"HowMuch ({format}, {formatProvider})";
         public string ToString(IFormatProvider provider) => $"HowMuch ({provider})";
         public string ToString(IFormatProvider provider, int significantDigitsAfterRadix) => $"HowMuch ({provider}, {significantDigitsAfterRadix})";