Function render 

pub fn render(
    frame: &mut Frame<'_>,
    area: Rect,
    palette: &Palette,
    limits: Option<(f64, f64)>,
    scale: ScaleMode,
    variable: Option<&str>,
)

Render a right-hand, vertical colorbar similar to a traditional Ncview legend. The bar is intentionally cell-based so it remains useful on terminals without sixel/kitty image support.