wip #43 add next time at to web UI

[vanboom]

This PR addresses issue #43, adding some human readable information "Next Run" information to the Web UI.

Method:

1. Parse the cron string using Fugit.parse_cron (no additional dependency required)
2. Display the Next Run column in the web UI, e.g. 10 hrs 20 min @ 10/06/2022 03:00

Thanks to the maintainers for a GREAT gem and for your consideration on this PR.

[mattyr]

@vanboom would you mind rebasing the pr against main? looks like a good addition, thanks!