echarts4r 0.3.3

Added echarts4rBox, renderEcharts4rBox, and echarts4rBoxOutput to create value boxes.
Fix e_common theme, was no longer applied due to dynamic dependencies introduced in 0.3.2
Fix e_flip_coords for timeline feature, see #166
name argument was not used in e_boxplot, see #171
Allow customising area under the curve of density plot see #172
Update mapbox dependency from 0.38 to 1.11
Fix country name conversion in e_country_names #189
Fix legend toggle in radar charts #74
e_loess, and e_lm take a model_args argument to pass arguments to underlying model function #194
Bump to JavaScript version to 4.9.0
echarts_from_json supports functions, see 199 (thanks to swsoyee)
Remove e_facet, was wrongly exported #212
Add tests, thanks to Etienne Bacher, see #201
Add styler, thanks to Wei Su see #211
Removed the {d3r} import: no longer necessary.

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