Like SaintsArrow but using Unity's default ArrowHandleCap to draw. (No dependency required)

Draw an arrow between different objects. The decorated field need to be a GameObject/Component or a Vector3/Vector2, or a list/array of them.

Parameters:

• string start = null: where does the arrow start. null for the current field.
• int startIndex = 0: when start is not null, and the start is a list/array, specify the index of the start.
• Space startSpace = Space.World: if the start is a Vector3/Vector2, should it be in world space or local space.
• string end = null: where does the arrow end. null for the current field.
• int endIndex = 0: when end is not null, and the end is a list/array, specify the index of the end.
• Space endSpace = Space.World: if the end is a Vector3/Vector2, should it be in world space or local space.
• EColor eColor = EColor.White: color
• float alpha = 1f: the alpha of the color. Not works with color.
• string color = null: the color of the line. If it starts with #, use html hex color, otherwise use as a callback. This overrides the eColor.
• float dotted = -1f: when >=0, draw dotted line instead.

Specially

1. using on an array/list without specifying start and end will arrow-connect the element from first to last.
2. startIndex & endIndex can be negative, which means to count from the end. -1 means the last element.

Example:

using SaintsField;

[SerializeField, GetComponent, DrawLabel("Entrance"),
 // connect this to worldPos[0]
 ArrowHandleCap(end: nameof(worldPos), endIndex: 0),
] private GameObject entrance;

[
    // connect every element in the list
    ArrowHandleCap(eColor: EColor.Green),
    // connect every element to the `centerPoint`
    ArrowHandleCap(end: nameof(centerPoint), eColor: EColor.Red),

    PositionHandle,
    DrawLabel("
quot; + nameof(PosIndexLabel)),
]
public Vector3[] worldPos;

[DrawLabel("Center"),
 PositionHandle
] public Vector3 centerPoint;

[DrawLabel("Exit"), GetComponentInChildren(excludeSelf: true),
 PositionHandle,
 // connect worldPos[0] to this
 ArrowHandleCap(start: nameof(worldPos), startIndex: -1),
] public Transform exit;

private string PosIndexLabel(Vector3 pos, int index) => 
quot;[{index}]\n{pos}";