add ScheduleTask

src/main/java/ghast/scheduler/JavaScheduleTask.java

@@ -0,0 +1,21 @@
+package ghast.scheduler;
+
+import lombok.RequiredArgsConstructor;
+
+import java.util.concurrent.Future;
+
+@RequiredArgsConstructor
+public class JavaScheduleTask implements ScheduleTask {
+
+	private final Future<?> future;
+
+	@Override
+	public boolean isCanceled() {
+		return future.isCancelled();
+	}
+
+	@Override
+	public void cancel() {
+		future.cancel(true);
+	}
+}