Missing ipywidgets in requirements.txt

[alimanfoo]

Description

I think ipywidgets might need to be added to the requirements.txt. I just tried out deploying on railway via this template and was getting errors relating to widgets like:

[Open Browser Console for more detailed log - Double click to close this message]
Failed to load view class 'ErrorWidgetView' from module '@jupyter-widgets/base'
Error: No version of module @jupyter-widgets/base is registered
    at _.loadClass (https://web-production-2492.up.railway.app/voila/static/7018.voila.js:1:77776)
    at _.loadViewClass (https://web-production-2492.up.railway.app/voila/static/7018.voila.js:1:74931)
    at https://web-production-2492.up.railway.app/voila/static/7018.voila.js:1:66785
    at async g.renderModel (https://web-production-2492.up.railway.app/voila/static/7018.voila.js:1:65329)

Adding ipywidgets resolved this.

Also looks like the version of voila is pinned and could be updated to a more recent release.

Reproduce

Try deploying on railway using this template repo, then try any of the notebooks that use widgets.