mergeGridR 0.2.0

• Added a standalone static HTML/WebGL export via export_static_app().
• Added an embeddable standalone applet article and pkgdown home-page iframe.
• Added configurable preview horizons, horizon-specific high scores, autoplay helpers, strategy benchmarks, and growth-focused lookahead support.
• Fixed cascade resolution so active-tile merges are followed by deterministic board-wide by-product merge scans until the board is stable. This keeps the Rcpp and standalone browser engines aligned when gravity creates adjacent equal-value tiles away from the active tile.