Multi-group pyramids, download button, footnotes on statgl_tables.

[emilmalta]

• statgl_plot() gains a position argument for bar/column charts: "stack", "percent", or "dodge" (bars side-by-side within each category). Supersedes stacking when both are set.
• statgl_plot() now accepts group = c(g1, g2) for two-variable pyramid charts. g1 determines the left/right pyramid split; g2 is the fill dimension — sub-bars coloured consistently across both sides with the legend showing only the g2 values. Combine with position to control layout: "stack" (default), "percent", or "dodge" (symmetric mirror around centre).
• statgl_plot() gains a download_data argument (default TRUE) that adds a context-menu button for downloading chart data as CSV/XLS or viewing it inline. Set FALSE to suppress.
• statgl_crosstable() and statgl_table() gain a .footnote argument. Pass a named character vector — names become bold titles, values the note text: c(\Note` = "Values are preliminary."). Replaces the old pattern of piping through kableExtra::footnote()`, which broke when these functions became htmlwidgets in 0.5.2.