Feature: Added Script for creating custom html with sidebar

[iamsukhe]

This PR adds an automated build script to convert lectures.md into a styled HTML page with a functional Table of Contents (TOC) sidebar.

✨ Key Changes

• Build Pipeline: Automates cleaning, theme exporting, and rendering in one command.
• Interactive TOC: Adds a toggleable sidebar that automatically lists headings (H1-H3).
• Custom Styling: Injects CSS for a dark-themed sidebar and improved image alignment.
• Mobile Support: Includes a responsive mobile menu with a dimmed background overlay.
• Deep Linking: Uses a custom renderer to add anchor IDs to all headings.

🚀 How to Run

• Run node build.js (or whichever name you gave the file).
• Find the output in the /dist folder.