Color fine alpha management

[adrien3d]

Hello, would it be possible to use custom colors (such as a HEX, or a RGB with alpha), for example for FormatColor?
I think we could use FormatColor::Custom(0x12_34_56) for custom color, but I don't see how to handle the alpha for transparency.
Do you have any idea on how to do so?

[jmcnamara]

The wrapped libxlsxwriter library only supports transparency for Chart Line and SolidFill elements.

These are exposed by the xlsxwriter.rs APIs: https://docs.rs/xlsxwriter/latest/xlsxwriter/index.html?search=transparency