ci: add GitHub Actions workflow to run tests on PRs

[tanmayjoddar]

Why

Running npm test automatically on pull requests increases trust and helps new contributors.

Where

• Add .github/workflows/ci.yml

Acceptance Criteria

• Workflow runs on push and pull_request
• Uses Node LTS (e.g. node-version: 20)
• Runs npm ci then npm test
• Fails the PR if tests fail

[Anushka904]

Hi @tanmayjoddar, I would love to work on this issue. Could you please assign it to me? I will create the GitHub Actions workflow according to the acceptance criteria.

[manya-singh7]

Hi @tanmayjoddar I'd like to be assigned to this. I am a GSSoC 2026 contributor.