ggpalettes 0.2.0

• Expanded the catalogue to 26 original categorical, sequential, and diverging palettes.
• Added pal_*() functions and named scale_color_*(), scale_colour_*(), and scale_fill_*() helpers for every palette.
• Added automatic discrete, continuous, and binned scale selection.
• Added gg_palette_info(), gg_palette_plot(), and gg_palette_check() for catalogue discovery, previews, and palette diagnostics.
• Added alpha, direction, and Lab/RGB interpolation controls.