Add DFM-17 notes to config.h for visibility

src/config.h

@@ -1,6 +1,11 @@
 #ifndef __CONFIG_H
 #define __CONFIG_H
 
+// Experimental support for Graw DFM-17 radiosondes added! Please test and report any issues!
+// WARNING: Using a DFM-17 as a primary flight tracker is NOT recommended yet!
+// NOTE: DFM-17 radiosondes require a GPS lock (and clear visibility to the sky) to calibrate its internal oscillator.
+// DFM-17 transmissions, especially APRS, may not decode correctly because of incorrect timing before the internal oscillator has been calibrated.
+
 // Define radiosonde type. Remove the "//" comment to select either RS41 or DFM17.
 //#define RS41
 //#define DFM17