xbsjCreateTransmitPolyline创建弧线说明

Cesium.xbsjCreateTransmitPolyline 根据 首末端点生成弧线，
参数有：
startPosition, 端点1
endPosition, 端点2
minDistance, 计算出的线段的最小间隔距离
heightRatio=1.0 弧线高度抬升程度，值越大，抬高得越明显
返回值是cartesian类型的坐标数组

使用示例：

```
var positionsCollection = p.map(e => {
const toDegree = 180.0 / Math.PI;
const cartesians = Cesium.xbsjCreateTransmitPolyline(e[0], e[1], 50.0, 5.0);
const poss = cartesians.map(ee => {
const carto = Cesium.Cartographic.fromCartesian(ee);
return [carto.longitude, carto.latitude, carto.height];
});

return poss;
});
```

The issue documents Cesium.xbsjCreateTransmitPolyline and includes a JavaScript usage example. Start by locating existing API documentation or examples for this function, then add the parameter, return-value, and arc-height explanations from the issue. Done means the function and example are documented clearly for users.

Written by the indexing model from the issue text.