[Warn] - IConvertable may cause data loss

[Liamth99]

Example of code diagnostic:

The following may cause data loss for certain member types (FP numbers to Integers for example) a warning should be shown for each of those members

[GenerateMapper(options: MappingOptions.AllowIConvertable)]
[Map<T1, T2>] // Where T1 has a floating point property that shares a name with a less precise Member on T2
public partial class MapperClass;