update compatibility matrix in README

Author: andydoro

README.md

@@ -31,7 +31,7 @@ Atmega328 @ 16MHz  |      X       |             |            |
 Atmega328 @ 12MHz  |      X       |             |            | 
 Atmega32u4 @ 16MHz |      X       |             |            | 
 Atmega32u4 @ 8MHz  |      X       |             |            | 
-ESP8266            |             |             |     X       | 
+ESP8266            |      X       |             |            | 
 Atmega2560 @ 16MHz |             |             |     X       | 
 ATSAM3X8E          |             |             |     X       | 
 ATSAM21D           |             |             |     X       |