Add test

[mo1ein]

I added tests for each chart.

• add line_test.go
• add boxplot_test.go
• add radar_test.go
• add tree_test.go
• add effectscatter_test.go
• add map_test.go
• add treemap_test.go
• add scatter_test.go
• add funnel_test.go
• add gauge_test.go
• add graph_test.go
• add heatmap_test.go
• add parallel_test.go
• add sunburst_test.go
• add themeriver_test.go

[Koooooo-7]

LGTM.