Add Dashboard for recently unarchived packages

[HenrikBengtsson]

Reviving @llrs idea of also showing which packages have been unarchived recently. In the past the dashboard presented "events", where both archived and unarchived events were shown. Then the dashboard was simplified to only show packages on CRANhaven. When this was done we lost information on what packages were recently unarchived.

I can imagine a second dashboard with unarchived packages with extra annotations such as archival and unarchival dates and versions, time on CRANhaven, etc. (Alternatively, we just redo the "raw data" table of events.)