lerp(v, alpha) {
    this.x += (v.x - this.x) * alpha;
    this.y += (v.y - this.y) * alpha;

    return this;
  }
Linearly interpolates this vector toward another vector.
@param {Vector2D} v - The target vector.
@param {number} alpha - The interpolation factor (0-1).
@returns {Vector2D} This vector.