Doc comment for platform macros

Author: clach04

src/c/watch_config.h

@@ -17,6 +17,7 @@
 //#define QUIET_TIME_IMAGE RESOURCE_ID_IMAGE_QUIET_TIME
 //#define QUIET_TIME_IMAGE_GRECT GRect(20, 20, 20, 20)  // Example assumes a 20x20 image
 
+// See https://developer.rebble.io/guides/best-practices/building-for-every-pebble/#available-defines-and-macros for hardware specific defines
 #ifdef PBL_ROUND /* 180x180 */
 /*TODO center/move right*/
     #define CLOCK_POS GRect(0, 52, 180, 180) /* probably taller than really needed */