decode method
Decodes a geohash to a (latitude, longitude) record. The result
is the exact center of the bounding box for the geohash, returned
by bounds function.
Implementation
({double lat, double lon}) decode(T geohash) {
final b = bounds(geohash);
return (lat: (b.minLat + b.maxLat) / 2, lon: (b.minLon + b.maxLon) / 2);
}