Dependency @turf/isolines has changed its API so version needs to be fixed

[mvl22]

The code calls isolines() at
https://github.com/mapbox/osrm-isochrone/blob/master/index.js#L20

However, that is using the pre-4.5.2 interface to @turf/isolines.

That interface was changed in:
Turfjs/turf@321d0df#diff-ba41233dbd590d55878b1d00a76de5b9
Turfjs/turf#781

Their example shows the difference:

- var isolined = turf.isolines(points, 'z', 15, breaks);
+ var isolines = turf.isolines(points, breaks, 'temperature');

So I think the version of @turf/isolines needs to be fixed as >=3.5.2 <4.5.2 at
https://github.com/mapbox/osrm-isochrone/blob/master/package.json#L32

or the calling code updated to the newer call format.

Subsequently the third parameter has been changed to an object, so is now set as the options.zProperty parameter:
https://github.com/Turfjs/turf/tree/master/packages/turf-isolines#isolines