ggtwotone - Dual-Tone and Contrast-Aware 'ggplot2' Geoms

Provides dual-stroke and contrast-aware extensions to 'ggplot2', designed for improved visibility and accessibility in complex visualizations. Includes geoms for dual-stroke segments, regression lines, curved annotations, function plots, paths, and adaptive text. Also includes utility functions for computing contrast-aware color pairs and perceptually distinct highlight palettes using WCAG-based contrast logic.