Add specific error names to 2.js; clarify let vs const in 2.s

Author: debug2604

Sprint-2/2-mandatory-errors/2.js

@@ -8,3 +8,6 @@ console.log(`I was born in ${cityOfBirth}`);
 //console.log(`I was born in ${cityOfBirth}`);
 //const cityOfBirth = "Bolton";
 //The error is that the variable should be declared as a constant before it is used in the console.log statement. 
+
+//This is a ReferenceError.
+//In this code, the key word does not need to be constant, it can be let - if this is the case the variable city0fBirth can be reassigned in other lines - instead of constant (which cannot reassign variable).