Add AUTHORS.md file listing contributors

[tomondre]

This pull request adds an AUTHORS.md file to acknowledge contributors to the Reana JupyterLab Extension. The contributors are listed in alphabetical order and were sourced from GitHub Insights.

[Copilot]

Pull Request Overview

This PR adds an AUTHORS.md file to acknowledge contributors for the Reana JupyterLab Extension.

• Introduces a new markdown file with a header and description
• Lists the contributors in alphabetical order

[garciagenrique]

Thanks for your first contribution @tomondre !