Update the calendar CSS to better serve the IVOA patterns #167

Currently #165 includes the calendar page layout we use for the scientific python project. However, most of the SP calendars are regular recurring ones, and thus their listing looks reasonable.

OTOH, for IVOA we'll have one-off meetings and therefore currently they show up as a separate line, and thus the list will become busy and not really useful. I would think we need to reconsider what listing would work, maybe even not list the individual meetings.

https://scientific-python.org/calendars/