Add function SyroVolcaSample_GetCurData()

[benwiley4000]

This is useful for keeping track of timestamps where different samples are located in the syro buffer, so you can give more detailed progress feedback to users. You can call SyroVolcaSample_GetCurData() anytime between SyroVolcaSample_Start() and SyroVolcaSample_End() to get the index of the SyroData currently being applied to the syro buffer.