Refactor : migrated empty_week.jsx to functional component

[Raman-Luhach]

What this PR does

This pull request refactors the empty_week.jsx component from a class-based component to a functional component.

Screenshots

Before

1. If timeline is empty and user can edit it, show info and links to get started.

2. If timeline is empty but user cannot edit, just note that timeline is empty.

   

3. If timeline is not empty, show the blackout week message.

After

1. If timeline is empty and user can edit it, show info and links to get started.

2. If timeline is empty but user cannot edit, just note that timeline is empty.

   

3. If timeline is not empty, show the blackout week message.

Open questions and concerns

I am a first-time contributor to Wikimedia and have converted empty_week.jsx to a functional component. If there are any issues with my pull request, please provide feedback, and I will address them promptly.

Thank you!

[ragesoss]

Please include before/after screenshots.