add downsampling example using minmaxlttb-rs #94

Job	Run time
Rustfmt	13s
Clippy	3m 49s
semver	41s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 1s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	2m 42s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	3m 16s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	6m 2s
Build Book	3m 18s
Build Wasm Examples (callback-example)	54s
Code Coverage	12s
Build Wasm Examples (basic)	53s
Build Examples (customization/consistent_static_format_export)	1m 24s
Build Examples (customization/density_mapbox_example)	23s
Build Examples (custom_controls)	31s
Build Examples (basic_charts)	28s
Build Examples (images)	42s
Build Examples (3d_charts)	30s
Build Examples (financial_charts)	31s
Build Examples (customization/multiple_plots_example)	28s
Build Examples (kaleido)	1m 20s
Build Examples (maps)	41s
Build Examples (ndarray)	30s
Build Examples (themes)	30s
Build Examples (shapes)	32s
Build Examples (scientific_charts)	27s
Build Examples (statistical_charts)	34s
Build Examples (subplots)	28s
	35m 0s

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