feat(layout): add `LayoutPolar` #99

Job	Run time
Rustfmt	14s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 25s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	6m 42s
Clippy	1m 56s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	3m 20s
Code Coverage	14s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 15s
Build Wasm Examples (callback-example)	52s
semver	42s
Build Book	3m 30s
Build Wasm Examples (basic)	52s
Build Examples (basic_charts)	36s
Build Examples (customization/consistent_static_format_export)	1m 24s
Build Examples (custom_controls)	34s
Build Examples (themes)	32s
Build Examples (scientific_charts)	30s
Build Examples (3d_charts)	29s
Build Examples (images)	56s
Build Examples (shapes)	29s
Build Examples (statistical_charts)	31s
Build Examples (customization/multiple_plots_example)	28s
Build Examples (maps)	42s
Build Examples (subplots)	29s
Build Examples (kaleido)	1m 26s
Build Examples (financial_charts)	26s
Build Examples (ndarray)	32s
Build Examples (customization/density_mapbox_example)	29s
	35m 35s

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