Add "Indoor" tag in FIT file

Having the “Indoor” and/or “Virtual” tag inside the FIT file would allow analysis platforms (TrainingPeaks —> WKO5, Intervals.icu) to easily differentiate between indoor and outdoor rides. I use WKO5 to analyze performance and now need to set the Indoor subsport activity for each individual workout performed indoors. Would be nice if this gets sorted automatically, which should work using the correct tag.