Calendar Widget

Uses Flutter's slivers for smooth, performant scrolling through calendar months, as emphasized in the key features for optimized rendering.

Provides a builder function (buildItem) to render each event, allowing full UI customization, as shown in the README example with GameCard.

Supports optional background images for the calendar and month headers, enabling enhanced visual design without complex code.

Allows intuitive scrolling forward and backward through months with an expandable header for day selection, as described in the philosophy.