Include a very basic, complete example as documentation?

Nobody has claimed this yet.

First: thanks for your excellent work!

I'm a HTML+JS noobie, and it would have helped me a lot to see a complete, minimal example, with just HTML+JS:

```html

Shapefile Export

Export Shapefile

function exportShapefile() {
// Sample data
var data = {
type: 'FeatureCollection',
features: [{
type: 'Feature',
properties: {
name: 'Some polygon'
},
geometry: {
type: 'Polygon',
coordinates: [[
[-64.8, 32.3], [-65.5, 18.3], [-80.3, 25.2], [-64.8, 32.3]]]
}
}]
};

// Save the zip file
shpwrite.zip(data, { outputType: "blob" }).then(function (zipBlob) {
saveAs(zipBlob, "my_shapefile.zip");
});
}

```
It can be run here: https://jsfiddle.net/pd14t8ew/2/

It's really not very different from the existing doc, but it took me a while to find the correct inputs.
If you're interested, I could write a corresponding PR for documentation.

Review the existing documentation and compare it with the complete HTML+JS example and jsfiddle.net link in the issue. Add a minimal runnable example showing the required inputs and shapefile export, then verify that a reader can follow it from a blank HTML file.

Written by the indexing model from the issue text.