List view, next event: Show countdown instead of date and time

[csete]

To be decided whether we want this or not.

https://community.libre.space/t/feature-request-move-aos-los-to-list-view-and-eliminate-upcoming-passes-view/2231

[jasonuher]

I'm interested in this too.

Would it be best to add it as an additional checkbox option in the list view?

1. The "Next Event" list item would remain unchanged
2. A new item "Next Event (T-)" would be added to the list that would exhibit this behavior.