Update the code sections in the NamasteJS notes

[sohamsshah]

The current code sections are written under normal code-block markdown using the three-backticks ```.

let x = [1,2,3]

As an enhancement; since all the codes are in JavaScript, we can use ```js
So that the code sections highlight JavaScript Keywords. See below example:

let x = [1,2,3]

[sohamsshah]

Close via #23