Better cache handling/invalidation

[paddymul]

Problem

When updating voila, users get stale 4321.voila.js files. This causes improper loading. To fix this we needed to send users complex cache clearing instructions.

Proposed Solution

It would be nice if the js build process appended a version number so new releases of voila had distinct filenames. That or a query-string cache buster. Even better if this is configurable via a setting so we can force cache busting with new releases.

Additional context

[trungleduc]

It would be nice if the js build process appended a version number so new releases of voila had distinct filenames.

I agree. A PR fixing this would be very welcome!