feat: Add {x,y}gap parameter to heatmaps #149

Job	Run time
semver	39s
Build Wasm Examples (basic)	58s
Code Coverage	10s
Rustfmt	17s
Tests (windows-latest, chrome, plotly_ndarray,plotly_image,static_export_chromedriver,debug)	8m 32s
Tests (ubuntu-latest, firefox, plotly_ndarray,plotly_image,static_export_geckodriver,static_expor...	3m 15s
Build Book	3m 52s
Tests (macos-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	4m 49s
Tests (ubuntu-latest, chrome, plotly_ndarray,plotly_image,static_export_default,debug)	3m 25s
Clippy	4m 33s
Build Wasm Examples (callback-example)	54s
Build Examples (3d_charts)	29s
Build Examples (kaleido)	1m 30s
Build Examples (customization/multiple_plots_example)	26s
Build Examples (themes)	32s
Build Examples (custom_controls)	27s
Build Examples (financial_charts)	31s
Build Examples (maps)	39s
Build Examples (customization/consistent_static_format_export)	1m 35s
Build Examples (images)	47s
Build Examples (statistical_charts)	28s
Build Examples (scientific_charts)	31s
Build Examples (basic_charts)	27s
Build Examples (ndarray)	31s
Build Examples (customization/density_mapbox_example)	29s
Build Examples (subplots)	30s
Build Examples (shapes)	28s
	41m 44s

Provide feedback