Adding country boundaries in PlotEquiMap()

Hi @nperez and @aho,

I am opening this issue to keep track of the improvement of PlotEquiMap() for adding the boundary of the countries in the maps.

As we have discussed in the meeting, there are two options:

• using map('world', interior = TRUE) is the easiest, and it plots the boundary of the countries automatically.

• giving the option for the users to plot their own shapefile. This could be very nice for the future in case we want to plot other boundaries (e.g., communities and provinces).

For now, I am plotting the boundaries by adding two lines in PlotEquiMap (this is the adapted version: https://earth.bsc.es/gitlab/cdelgado/cdelgado_copernicus/-/blob/development_branch/FOCUS/PlotEquiMap_countries.R#L941). I am using Chung's file with the boundaries, but I have it in RDS format. @cchou, could you please let us know where is the original shapefile?

This issue is related to #8 (closed).

Thank you very much,

Carlos @cchou