Set cell-index attribute as a string

[jtpio]

References

Currently Voila produces HTML with cell-index attributes set to integers:

This can for example be seen on Binder: https://mybinder.org/v2/gh/voila-dashboards/voila/main?urlpath=voila%2Ftree%2Fnotebooks

However attributes are more commonly set as string.

Also Voici expects a string when looking up these elements here: https://github.com/voila-dashboards/voici/blob/7b8825e10c05e31e4e1731fffbe60ffdc327304e/packages/voici/src/app.ts#L328

const element = document.querySelector(`[cell-index="${idx + 1}"]`);

Code changes

Update cell-index to be a string in the templates.

User-facing changes

None

Backwards-incompatible changes

None

[github-actions]

👈 Launch a Binder on branch jtpio/voila/cell-index

[trungleduc]

Thanks @jtpio