docs: add pull request template

[Arvuno]

Summary

• Added .github/PULL_REQUEST_TEMPLATE.md to guide contributors on writing good PR descriptions.

Problem

The repository lacks a pull request template, leading to low-quality or incomplete PR descriptions that make review harder.

Evidence

Issue #356 explicitly requests adding a PR template. CONTRIBUTING.md references PR templates but none exist.

Solution

Created .github/PULL_REQUEST_TEMPLATE.md with sections for: What does this PR do, Motivation, How to test, and Checklist. Also noted that existing issue templates (.github/ISSUE_TEMPLATE/) already exist and were not modified.

Tests / Validation

• Verified file exists at correct path: .github/PULL_REQUEST_TEMPLATE.md
• Verified it follows GitHub's expected template format
• Did not modify existing issue templates

Risk / Compatibility

Docs/tooling only — no code changes, no runtime impact.

Notes for maintainers

• Existing issue templates (bug_report.md, custom.md, feature_request.md) were left unchanged
• Template format follows GitHub best practices

[vercel]

Someone is attempting to deploy a commit to the Darshan Rajput's projects Team on Vercel.

A member of the Team first needs to authorize it.

[Darshan3690]

Thanks for the contribution.

For future contributions, please follow the project's contribution workflow:

Open an issue first and clearly describe the problem, improvement, or feature you would like to work on.
Wait for a maintainer to review the issue and assign it to you.
After the issue is assigned, create a branch, implement the changes, and open a pull request linked to that issue.

This helps avoid duplicate work and ensures that contributions align with the project's roadmap before development begins.

Since this PR was opened without a prior assigned issue, please open an issue first for discussion next time.

Thank you for your interest in contributing.

[Arvuno]

Acknowledged on the issue-first workflow — got it for future contributions. The change in this PR is small (template / metadata / unused-import cleanup) and the docs pattern followed what the README already had, but I should have opened an issue first to align with your contribution policy. I'll do that going forward.

If you'd like, I can close this PR and re-open it against a tracking issue — let me know.