List layers in a datasource
st_layers(dsn, options = character(0), do_count = FALSE)
data source name (interpretation varies by driver - for some drivers,
dsn is a file name, but may also be a
folder, or contain the name and access credentials of a database)
character; driver dependent dataset open options, multiple options supported.
logical; if TRUE, count the features by reading them, even if their count is not reported by the driver