Update README.md

Co-authored-by: per1234 <[email protected]>

Author: facchinm

README.md

@@ -43,7 +43,7 @@ The backbone of the packaging process is the https://github.com/arduino/ArduinoC
 
 It can be used for a variety of tasks including:
 
-**Recompiling libmbed with source level debug support**
+### Recompiling libmbed with source level debug support
 
 ```
 cd $sketchbook/hardware/arduino-git/mbed