Use visual_file_name (csv's name) instead of geo_file_name for output

[adisidev]

cartogram-cpp/src/main.cpp

Line 73 in 85068c7

std::string map_name = cart_info.set_map_name(geo_file_name);

[adisidev]

One input geo_file could result in multiple cartograms depending on the CSV file it is used with. However, each CSV would only correspond to one output cartogram. Thus, the unique output identifier would be the csv's name, not the map file's name.

For example, australia_by_state_and_territory_since_1942_cartogram.geojson vs australia_population_2021_cartogram.geojson: the latter is far better.