feat: add DensityMap trace for the MapLibre map subplot (#416) #233

Job	Run time
Build Book	5m 32s
Build Wasm Examples (basic)	57s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	8m 4s
semver	50s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	3m 43s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 21s
Build Wasm Examples (callback-example)	1m 5s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	4m 19s
Build Examples (kaleido)	1m 21s
Clippy	6m 59s
Rustfmt	14s
Build Examples (financial_charts)	39s
Build Examples (ndarray)	33s
Build Examples (maps)	45s
Build Examples (scientific_charts)	33s
Build Examples (themes)	34s
Build Examples (customization/density_mapbox_example)	33s
Build Examples (customization/multiple_plots_example)	36s
Build Examples (statistical_charts)	57s
Build Examples (subplots)	29s
Build Examples (images)	50s
Build Examples (3d_charts)	35s
Build Examples (basic_charts)	39s
Build Examples (shapes)	34s
Build Examples (customization/consistent_static_format_export)	1m 44s
Build Examples (custom_controls)	38s
Code Coverage	19s
	47m 23s

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