Halo (atmospheric glow) configuration for the globe.
When enabled, renders a radial gradient-based glow around the globe. Requires globe projection to be visible. Prefer setting via map options at initialization or dynamically via MTStyle.setHalo.
Defines the radial gradient as a list of stops, each as a pair of normalized position (0..1) and a CSS color string (e.g., "transparent", "#RRGGBB", "rgba(r,g,b,a)").