Package-owned, backend-independent layout settings. Child charts retain
separate ECharts options (EChartsOption in src/export/option.ts); this
layout does not merge or renumber their axes, series, or legends.
Rows fill from left to right, with equally sized cells. Unused final cells
remain empty. Settings serialize as ordinary JSON with to_list().
Examples
to_list(setup_PanelLayout(ncol = 2))#> $ncol
#> [1] 2
#>
#> $gap
#> [1] 12
#>
#> $padding
#> [1] 0
#>