Update README.md

Author: danielnilsson9

README.md

@@ -16,7 +16,7 @@ The virtual port (Serial) is used for communication with the computer (flashing
 
 You need to make three connections to the Renesas MCU.
 
-TOOL0 -> RX & TX of Serial (Connect to both joinig them together)  
+TOOL0 -> RX & TX of Serial (Connect to both joining them together)  
 RESET -> D9  
 FLMD  -> D10