Compound Timeline: review 'today' marker line design

[k9dh3zij]

The compound timeline offers the option to mark 'today' using a single line that runs through the middle of the day.

Some services split the day into 4 quarters therefore showing a line can be confused as marking a specific quarter of that day.

NSS have designed a 'today' marker that highlights the entire day - we may want to adapt our marker to utilise that.

[github-actions[bot]]

This issue has been marked as stale because it has been open for 60 days with no activity