Add a new `CoverflowMode.roulette` (or `CoverflowMode.arc`) preset option to the package.

[GalaxyPhoenix716]

Visual Behavior (Top-Pivot Arch):
This mode arranges and fans the cards along a curved arch hanging from a top pivot (as shown in the attached layout sketch):

• Z-axis Rotation (Fanning): Cards rotate in the 2D screen plane (Z-axis). Left-side cards rotate counter-clockwise, and right-side cards rotate clockwise, using Alignment.topCenter as the pivot so they fan out at the bottom.
• Y-translation (Crescent Path): Cards translate vertically upward on the Y-axis as they move away from the center.

New Parameters:

1. rouletteRadius (double):

   • Controls the radius of the fanning circle.
   • A smaller radius creates a tight, steep arch (fewer visible cards, aggressive tilt).
   • A larger radius creates a flat, wide arch (more visible cards, subtle tilt).

2. roulettePerspective (double):

   • Controls the 3D depth perspective distortion (e.g., setting the [3, 2] matrix entry to values like 0.001 or 0.002).
   • If set to 0.0, it acts as a flat 2D fanned arc.
   • If set to a value greater than 0.0, it adds Y-axis or X-axis tilt perspective, making the arc feel like a 3D turntable rotating in virtual space.

Example Code Concept:

CoverflowCarousel.builder(
  mode: CoverflowMode.roulette,
  rouletteRadius: 600.0,      // Curvature radius
  roulettePerspective: 0.001, // 3D depth perspective
  ...
)