docs: add Table of Contents to README (JhaSourav07#974)

## Description

Fixes JhaSourav07#972

This PR adds a Table of Contents (TOC) to the main `README.md` to
improve navigation for users and contributors. The TOC is placed at the
top after the tagline and links to all major sections (Design
Philosophy, Live Demo, Theme Presets, FAQ, etc.), mirroring the
structure already used in `CONTRIBUTING.md`.

## Pillar

- [ ] 🎨 Pillar 1 — New Theme Design
- [ ] 📐 Pillar 2 — Geometric SVG Improvement
- [ ] 🕐 Pillar 3 — Timezone Logic Optimization
- [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview

N/A – Documentation change only.

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [ ] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
- [ ] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will fail otherwise).
- [x] My commits follow the Conventional Commits format (e.g.,
`feat(themes): ...`, `fix(calculate): ...`).
- [ ] I have updated `README.md` if I added a new theme or URL
parameter.
- [ ] I have started the repo.
- [x] I have made sure that i have only one commit to merge in this PR.
- [ ] The SVG output matches the CommitPulse "premium quality" aesthetic
standard (no raw elements, smooth animations, correct fonts).
- [ ] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

README.md

@@ -14,6 +14,25 @@
 
 > **Drop this into your GitHub profile README and stop being boring.**
 
+## 📖 Table of Contents
+
+- [Design Philosophy](#the-isometric-monolith--design-philosophy)
+- [Live Demo](#live-demo)
+- [Deep Customization](#deep-customization--url-parameters)
+- [Theme Presets](#theme-presets)
+- [Theme Preview Gallery](#theme-preview-gallery)
+- [Real-Time Accuracy](#real-time-accuracy--the-contribution-count-problem)
+- [Architecture & Tech Stack](#architecture--tech-stack)
+- [Self-Hosting](#self-hosting-in-4-steps)
+- [Automated Contributor Workflow](#automated-contributor-workflow)
+- [FAQ](#faq)
+- [Contributing](#contributing)
+- [License](#license)
+- [Themes](#themes)
+- [Contributors](#contributors)
+
+---
+
 ![CommitPulse Live Demo](https://commitpulse.vercel.app/api/streak?user=jhasourav07&theme=neon)
 
 [![Join CommitPulse Discord](https://img.shields.io/badge/Join-CommitPulse%20Discord-5865F2?style=for-the-badge&logo=discord&logoColor=white)](https://discord.gg/Cb73bS79j)