feat(layout): add `LayoutPolar` #100

Job	Run time
Rustfmt	17s
Clippy	4m 6s
semver	42s
Build Wasm Examples (callback-example)	54s
Build Wasm Examples (basic)	52s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	6m 31s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 16s
Code Coverage	13s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 45s
Build Book	3m 34s
Build Examples (3d_charts)	32s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	3m 6s
Build Examples (custom_controls)	32s
Build Examples (customization/density_mapbox_example)	24s
Build Examples (customization/multiple_plots_example)	27s
Build Examples (financial_charts)	32s
Build Examples (kaleido)	1m 16s
Build Examples (themes)	31s
Build Examples (ndarray)	30s
Build Examples (scientific_charts)	27s
Build Examples (customization/consistent_static_format_export)	1m 23s
Build Examples (statistical_charts)	31s
Build Examples (images)	52s
Build Examples (maps)	37s
Build Examples (basic_charts)	33s
Build Examples (shapes)	33s
Build Examples (subplots)	30s
	37m 26s

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