Vega-Lite -如何绘制箭头？

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "绘制带箭头的线段",
  "data": {
    "values": [
      {"x": 50, "y": 50, "angle": 45, "length": 50},
      {"x": 100, "y": 100, "angle": -30, "length": 100}
    ]
  },
  "mark": {"type": "line", "strokeWidth": 2},
  "encoding": {
    "x": {"field": "x", "type": "quantitative"},
    "y": {"field": "y", "type": "quantitative"},
    "angle": {"field": "angle", "type": "quantitative"},
    "length": {"field": "length", "type": "quantitative"}
  },
  "transform": [
    {"calculate": "datum.x + datum.length * cos(PI * datum.angle / 180)", "as": "x2"},
    {"calculate": "datum.y + datum.length * sin(PI * datum.angle / 180)", "as": "y2"}
  ],
  "mark": {
    "type": "rule",
    "clip": true,
    "tooltip": true
  }
}