[Docs]: Add Screenshots/Demo header to PULL_REQUEST_TEMPLATE.md

[eileenchua]

---

⚠️ Before You Contribute: Please Review These Guidelines ⚠️

Thank you for your interest in contributing! Before you ask to be assigned, please understand our workflow:

1. Do not start work before being assigned.
2. Wait for a maintainer to assign this issue to you. Just posting a comment does not count as an assignment.
3. We reserve women-devs-only issues for women developers. As our mission is to empower women in tech, we hold this space for them.

This process ensures fairness and helps us uphold our community's mission. Thank you for your understanding!

---

Describe the Issue
Contributors should provide screenshots and/or videos of their changes to facilitate pull request reviews.

Proposed Changes
Update PULL_REQUEST_TEMPLATE.md to include a section for contributors to attach their screenshots/video demo of their changes.

## Screenshots/Demo
<!-- If applicable, add screenshots or demo GIFs to help explain your changes -->

You may refer to our other repo to ensure alignment: https://github.com/Women-Devs-SG/volunteer-telegram-bot/blob/main/.github/pull_request_template.md

Additional Context
N/A

[diptipradeep]

Hi @eileenchua I would like to work on this issue? Could you please assign it to me .

[eileenchua]

Hello @diptipradeep, just assigned this to you!