Arrow/Ray shape

[nixon-voxell]

Goal

Ability to create an arrow shape that is appended on the ends of VelloLine or VelloBezPath.

Example: https://motioncanvas.io/api/2d/components/Ray

Proposed Solution

/// Attach an arrow head to the end of a [`VelloBezPath`] or [`VelloLine`].
#[derive(Component, Clone, Copy)]
pub struct ArrowHead {
    pub shape: ArrowShape,
    /// Size of the arrow.
    pub size: f32,
    /// Offset of the arrow from the origin point (0 - 1 to stay within the path).
    pub offset: f32,
    /// Rotation offset of the arrow from the original tangent direction of the path.
    pub rotation_offset: f32,
}

pub enum ArrowShape {
    Triangle,
    Line,
    Point,
}

We also need a sensible default for these arrows:

impl Default for ArrowHead {
    fn default() -> Self {
        Self {
            shape: ArrowShape::Triangle,
            size: 10.0,
            offset: 0.0,
            rotation_offset: 0.0,
        }
    }
}