how to split a LineString into two LineStrings

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**maptalks's version and what browser you use?**
----

maptalks v0.37.0
Google Chrome
**Issue description**
----
I need two split a existed LineString, into Two Line Strings from where the user right clicks and choose the split option. I wonder if there is way for it. Any help would be appreciated. Thank you.
this is my function for split:
` this.splitLineString = function (coordinate, target) {
new maptalks.Marker(
coordinate,
{
'symbol': {
'markerType': 'ellipse',
'markerFill': '#ffffff',
'markerLineColor': '#e65100',
'markerLineWidth': 3,
'markerWidth': 5,
'markerHeight': 5
},
}
).addTo(draw_layer);
console.log(target)
}`
and this is the code which makes the LineString:
`if (param.geometry.type === 'LineString' && FreeLineMode === true) {

var GisSymbol = param.target.options.symbol.tag.GisSymbol;

var dg = drawTool.getCurrentGeometry();
if (dg != null) {
line = new maptalks.LineString(
dg.getCoordinates(),
{
tag: {
GisSymbolId: GisSymbol.GisSymbolId,
GisInfoGuid: guid(),
GisInfoId: null,
GisSymbolSeqNum: GisSymbol.GisSymbolSeqNum,
IsNew: true,
Element: GisSymbol,
Label: null
},
symbol: {

'lineColor': 'red',
'lineWidth': 2,
'lineJoin': 'round',
'lineCap': 'round',
//'lineDasharray': lineDasharray,
//'lineOpacity': {
// stops: [[GisSymbol.GisSymbolZoomStart, 0], [GisSymbol.GisSymbolZoomStop, 1]]
//},
'textPlacement': 'line',
'textSize': 12,
'textDy': -20,
'textFaceName': 'sans-serif',
//'textName': "" + element.ItemLength + " m",
'textWeight': 'normal',
'textStyle': 'normal',
'textFill': '#000',
//'textOpacity': { stops: [[GisSymbol.GisSymbolZoomStart, 0], [GisSymbol.GisSymbolZoomStop, 1]] },
'textHaloFill': '#fff',
//'textOpacity': { stops: [[GisSymbol.GisSymbolZoomStart, 0], [GisSymbol.GisSymbolZoomStop, 1]] },
'textWrapCharacter': '\n',
'textLineSpacing': 0,
'textHorizontalAlignment': 'middle',
'textVerticalAlignment': 'middle',
'textAlign': 'center'
},

}
);
draw_line_layer.addGeometry(line);
}

}`

Start with the splitLineString function, the drawTool.getCurrentGeometry call, and the LineString construction shown in the issue. Review the LineString geometry APIs and determine how the right-click coordinate should divide the existing coordinates; done means producing two LineStrings at the selected location. No repository file or test is named.

Written by the indexing model from the issue text.