feat(curriculum): added a short explanation on ES6 for isNan lesson (#62592)

Co-authored-by: Huyen Nguyen <25715018+huyenltnguyen@users.noreply.github.com>

curriculum/challenges/english/blocks/lecture-working-with-numbers-and-common-number-methods/672d26809d388621ad1ecd43.md

@@ -43,7 +43,7 @@ console.log(isNaN("blabla"));  // true: "blabla" is not a number
 
 As you can see, `isNaN()` first attempts to convert the parameter to a number. If it can't be converted, it returns `true`. This behavior can lead to some surprising results, especially when dealing with strings that can be coerced into numbers.
 
-Due to these potential inconsistencies, ES6 introduced `Number.isNaN()`. This method does not attempt to convert the parameter to a number before testing. It only returns `true` if the value is exactly `NaN`:
+Due to these potential inconsistencies, ES6 (the sixth edition of JavaScript, released in 2015) introduced `Number.isNaN()`. This method does not attempt to convert the parameter to a number before testing. It only returns `true` if the value is exactly `NaN`:
 
 ```js
 console.log(Number.isNaN(NaN));        // true