turf-nearest-point: maintain point properties in result type

[EmilJunker]

This PR improves the NearestPoint type and the type definition for the nearestPoint function.

Consider the following example in TypeScript:

const coordinatesList = [[0, 0], [1, 1], [0, 1]];
const pointsList = coordinatesList.map((coordinate, i) => {
    return turf.point(coordinate, {
        name: `point${i}`
    });
});
const pointsCollection = turf.featureCollection(pointsList);
const myNearestPoint = turf.nearestPoint(turf.point([2, 2]), pointsCollection);

With the old behaviour myNearestPoint.properties.name is of type any according to TypeScript.

With the changes in this PR, the type of myNearestPoint.properties.name is correctly inferred as string.

This change should be non-breaking.

This PR replaces #2861.

Please provide the following when creating a PR:

• Meaningful title, including the name of the package being modified.
• Summary of the changes.
• Heads up if this is a breaking change.
• Any issues this resolves.
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[twelch]

Confirmed in light testing that user-provided properties are properly flowing through to the returned type, while also picking up featureIndex and distanceToPoint.

[twelch]

Thank you @EmilJunker for improving this. It will become available in the next release, timing TBD.