Minor refactor, print STDERR in red

Author: earlephilhower

README.md

@@ -7,7 +7,7 @@ LittleFS uploader compatible with Arduino IDE 2.2.1 or higher. For use with the
 
 ## Usage
 
-`[Ctrl]+[Shift]+[P]`, then "`Upload LittleFS to Pico/ESP8266`"
+`[Ctrl]` + `[Shift]` + `[P]`, then "`Upload LittleFS to Pico/ESP8266`"
 
 ## Glitches