Reduce scope of compatibility to tested boards

Author: aliphys

README.md

@@ -39,7 +39,7 @@ The Arduino_UnifiedStorage library provides a unified interface to access differ
 * Format partitions and drives (FAT and LittleFS)
 
 ## Compatibility
-This library is compatible with STM32 and Renesas based Arduino boards. The availability of storage mediums depends on the hardware interfaces:
+This library has been tested with the following STM32 and Renesas based Arduino boards. The availability of storage mediums depends on the hardware interfaces:
 * Portenta Machine Control: USB and Internal QSPI Flash
 * Portenta H7 + Portenta Breakout: USB, SD, and QSPI
 * Portenta H7 + Vision Shield: SD and QSPI