Support headers when downloading appcast

I just migrated fom Winsparkle because I needed fine grained control over download and it worked like a charm. However I noticed a little feature which helped me to figure out users how many users didn't upgrade yet. WinSparke used to set the user agent with the app name and version for the appcast get request. Would you mind adding a property to set the headers to pass to the inner HttpClient so achieve the same feature?