feat: add React business document library sample

[vystartasv]

By submitting this pull request, you agree to the contribution guidelines

• New sample
• Bug fix/update
• Related ...[truncated]

[vystartasv]

Hi maintainers and community 👋

Could someone with access to a SharePoint Online tenant help validate this sample and capture one or two representative screenshots?

The sample is a read-only Business Document Library browser with configurable library/folder scope, folder navigation, breadcrumbs, file type and modified-date columns, safe SharePoint open/download links, refresh, and bounded metadata loading.

Helpful checks:

• Configure it against a small SharePoint document library or folder.
• Verify folder navigation, breadcrumbs, refresh, empty state, permissions, and error handling.
• Check file open/download links, narrow-viewport rendering, and keyboard operation.
• Capture one or two screenshots suitable for the README.

Dummy data is completely fine. Please remove or blur tenant names, site URLs, file names, user names, and any other sensitive information before sharing screenshots. The README includes setup and validation steps.

The sample builds, tests, and packages locally, but I do not currently have a tenant available for end-to-end validation. Any observations would greatly help complete the pull request. Thank you!

[github-actions]

Sample PR validation for #6477

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
README.md contains visitor stat image	✅ Succeeded
Sample requires a .nvmrc file	✅ Succeeded
Sample requires a README.md	✅ Succeeded
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded
No upgrade reports	✅ Succeeded

@vystartasv please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.