docs: add new question about == and === in JavaScript

[vardhan30016]

Added New Question: Difference Between == and === in JavaScript

Description:
This pull request adds a new JavaScript interview question explaining the key difference between == (loose equality) and === (strict equality), including examples and best practices.

Example Code:

console.log(5 == '5');   // true
console.log(5 === '5');  // false

[sudheerj]

@vardhan30016 I think this question is already present.