Update readString.adoc minor formating

Author: Akshay Sharma

Language/Functions/Communication/Serial/readString.adoc

@@ -12,7 +12,7 @@
 
 [float]
 === Description
-Serial.readString() reads characters from the serial buffer into a string. The function terminates if it times out (see link:setTimeout{ext-relative}[setTimeout()]).
+`Serial.readString()` reads characters from the serial buffer into a string. The function terminates if it times out (see link:setTimeout{ext-relative}[setTimeout()]).
 
 This function is part of the Stream class, and is called by any class that inherits from it (Wire, Serial, etc). See the link:stream{ext-relative}[Stream class] main page for more information.