Add description and proper hyper links for topics

[Saiharitha3]

The current documentation for the JavaScript guide needs improvements to ensure clarity and completeness. Specifically, the following updates are requested:

Add detailed descriptions for each topic to improve readability and provide context for readers. Incorporate proper hyperlinks to relevant resources (like MDN, official documentation, and tutorials) to enhance usability and offer additional learning opportunities.

[Saiharitha3]

Hi @aviraw please assign this issue to me and add hacktoberfest label to it