[BUG] MultiLineString features are consolidated into a single feature

Nobody has claimed this yet.

If you pass .zip() an array of multilinestring features, the lines are consolidated into a single feature.

For the features below, I would expect a shapefile with two independently selectable features. However, they are unified into a single feature. I haven't seen this same issue when working with points

```
const features = [
{type:"Feature",geometry:{type:"MultiLineString",coordinates:[[[-118.429159,33.997878],[-118.429407,33.998196]],[[-118.429797,33.998696],[-118.429904,33.998833]],[[-118.428464,33.996969],[-118.428366,33.99686],[-118.42825,33.99675],[-118.428044,33.99658]],[[-118.428464,33.996969],[-118.428583,33.997131],[-118.428833,33.997472]]]}},
{type:"Feature",geometry:{type:"MultiLineString",coordinates:[[[-118.403108,34.01443],[-118.403007,34.014388]]]}}
]

const dataforZip = {
type: "FeatureCollection",
features: features,
options
}

const zipData = await shpwrite.zip(
dataforZip,
options
);
```

The output geometry from the above is:

`
{"type":"MultiLineString","coordinates":[[[-118.429159,33.997878],[-118.42940700000001,33.998196]],[[-118.429797,33.99869600000001],[-118.429904,33.998833]],[[-118.42846399999999,33.996969],[-118.42836599999998,33.99686],[-118.42825000000002,33.996750000000006],[-118.42804400000001,33.99658]],[[-118.42846399999999,33.996969],[-118.428583,33.997131],[-118.428833,33.997472]],[[-118.40310800000002,34.01443],[-118.403007,34.014388]]]}`

Start by reproducing the issue with the supplied FeatureCollection and the shpwrite.zip entry point, then trace how MultiLineString features are converted for shapefile output. Done means the two input features remain independently selectable rather than being combined into one output feature.

Written by the indexing model from the issue text.