Don't throw error if geojsonhint fails

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**mapbox-gl-js version**: 0.52.0
**mapbox-gl-draw version**: 1.1.1

### Steps to Trigger Behavior

1. Add some geojson (with `draw.add()`) that gets errors with `geojsonhint`.

### Expected Behavior
Often, geojson will fail geojsonhint but still be displayable. In these cases, it is preferable to see the geojson than it is to just get a console error and see nothing.

### Actual Behavior
The operation fails and I can't see my data.

### Suggestion

Instead of throwing an error, just log one, like so:
```js
const errors = geojsonhint.hint(geojson, { precisionWarning: false }).filter(e => e.level !== 'message');

if (errors.length) {
console.error('There were errors parsing your geojson, it may not display correctly', errors);
}
```

You could even throw up an `alert` if you were _really_ worried about accidentally misrepresenting some data.

I'm sorry I don't have an example, I only have a 20 MB file. In this file, two of the 38,000 features fail with the error "a LinearRing of coordinates needs to have four or more positions". I have no idea how I would even find these. But if I disable the error throwing I can load the file just fine and render the file to the map.

Start at the draw.add() path and find where geojsonhint.hint() errors are handled. Verify that invalid-but-displayable GeoJSON is still rendered while the validation problem is logged instead of stopping the operation; add or update a focused test if the relevant test location is found.

Written by the indexing model from the issue text.