We’re actively working on this. Stay tuned for more updates.
If you’d like to contribute to our thinking and help shape this feature, please write to me at hnarayan(at)adobe(dot)comToon commented
Yes add this feature to the shared document.
At this moment there are some plugins that allow you to copy CSS form the XD file.
This is nice, but it would be even more nice if this could be done form the shared XD document ('Share for Development').
And please, just as with the different color modes you can choose from, let developers choose form px, em and rem for font-sizes.
Or just rework the PSD Extract feature, that is available in Dreamweaver, to an XD Extract feature for shared documents.