Add turf.difference and turf.union

Hello, this port is very nice overall but it would be nice if it could have the difference and union transform operations. We have a product using turfJs and we have a new product that is processing a shape file and converting it to t geoJson. Part of this is calculating the area, we want to match the area calculation algorithm to match our js implementation but the lack of the difference and union operations is preventing us from doing so at the moment.

まず、Java SDK における既存の Turf および GeoJSON 操作のエントリポイントを特定し、Turf.js の difference と union の動作と比較します。shape-file から GeoJSON への変換と面積計算のユースケースを受け入れ条件の文脈として使用します。両方の操作が利用可能で、このワークフローに対して一致する結果を生成すれば完了です。