Detects chart orientation from the echarts4r object.
ro_e_detect_axis_orientation.RdReturns "horizontal" for column/line charts (categories on xAxis) and "vertical" for bar charts (categories on yAxis after e_flip_coords()).
ro_e_detect_axis_orientation.RdReturns "horizontal" for column/line charts (categories on xAxis) and "vertical" for bar charts (categories on yAxis after e_flip_coords()).