feat(layout): add `LayoutPolar` #88

Job	Run time
Clippy	3m 57s
semver	38s
Rustfmt	15s
Build Wasm Examples (callback-example)	53s
Build Wasm Examples (basic)	52s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	10m 14s
Code Coverage	10s
Build Book	3m 23s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 3s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	6m 17s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 19s
Build Examples (3d_charts)	33s
Build Examples (basic_charts)	36s
Build Examples (customization/consistent_static_format_export)	1m 17s
Build Examples (custom_controls)	33s
Build Examples (customization/density_mapbox_example)	30s
Build Examples (customization/multiple_plots_example)	26s
Build Examples (financial_charts)	31s
Build Examples (shapes)	31s
Build Examples (images)	49s
Build Examples (maps)	42s
Build Examples (scientific_charts)	24s
Build Examples (ndarray)	30s
Build Examples (kaleido)	1m 17s
Build Examples (themes)	30s
Build Examples (statistical_charts)	37s
Build Examples (subplots)	28s
	43m 15s

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