sponsor more

Hi there,

I was just marking up another project and I ran into a limitation of the
sponsor property, as this is only used on MedicalStudy, I get another red
warning in sdtt. I would like to markup an Organization that is the sponsor
of another Organization (charity) or an event.
Example: https://gist.github.com/daarom/166764c876d58870247f

I assume schema should be expanded to make this possible, correct?

If this is correct, where do I make a request to make such
changes/improvements?

thanks :)

Vincent