Larger marker size in time series plot

[emmanuelle]

Since we have a large number of countries and a limited set of colors, marker symbols are useful to distinguish between countries. However they are quite small at the moment. One would have to check both on laptop and mobile screen to choose the optimal marker size.

See https://github.com/covid19-dash/covid-dashboard/blob/master/make_figures.py#L60 for the definition of scatter traces and https://plotly.com/python/marker-style/ for changing the marker size.

[KranthiGV]

I would like to take this up. To confirm, the task at hand is to set marker_size to an appropriate value determined by eyeballing the marker sizes in both laptop and mobile. We agree that the default size now is too small even for a laptop screen.