chore: add descriptions to root, frontend, and backend package.json files

[Harshbansal06]

Added missing description fields to root, frontend, and backend package.json files. Closes #7

What

This PR adds informative description fields to the package.json files in both the frontend and backend directories. It also updates the root package.json description to better reflect the project's purpose as a ride-sharing web application for IIIT Jabalpur students.

Fixes #7

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update

Proof of work

• Added "description": "Splitt backend API" to backend/package.json
• Added "description": "Splitt frontend" to frontend/package.json
• Updated description to "Splitt - A ride-sharing web application for IIIT Jabalpur students." in the root package.json

Checklist

• I claimed this issue before starting work
• Branch name follows the convention (feature/, fix/, docs/)
• Commits follow Conventional Commits format
• CI is passing (lint, prettier, build)
• I have self-reviewed my own code
• Any non-obvious decisions are explained with a comment in the code

[BitForge95]

LGTM!

[Harshbansal06]

Thank you for the review! Let me know if anything else is needed before merging.