Nullable Decimals Don't Write Correctly with a `0;00` Format

[joseph-chew]

When trying to write to a file with a class that has a decimal? property and a format like 0;00 or 0;000, the values to the right of and including the decimal seem to be getting dropped.

Setup for Reproduction (.NET 6)

1. Create a file that has a number value (one field should do)
   a) Example: 0000002340
2. Create a class that has a decimal? property:

public record TestClass
{
    [FixedWidthLineField(Start = 1, Length = 10, Pad = '0', PadSide = PadSide.Left, Format = "0;00")]
    public decimal? TestProperty { get; init; } = default;
}

3. Read the file into memory, then write the file again.

List<string> readData = File.ReadAllLines(@"PATH_TO_TEST_FILE").ToList();
TestClass testClass = new FixedWidthLinesProvider<TestClass>().Parse(readData).First();

// `testClass.TestProperty` should equal `23.4` after parsing the readData

var writeData = new FixedWidthLinesProvider<TestClass>().Write(new() { testClass });
File.WriteAllLines(@"PATH_TO_NEW_FILE");

4. Check the newly created file and notice it's 0000000023 instead of the expected 0000002340