add playtime field to UserScore

sekai-scores-db/build.gradle

@@ -1,5 +1,6 @@
 plugins {
 	id 'java'
+	id 'java-library'
 }
 
 group 'cc.sukazyo'

src/main/java/cc/sukazyo/sekai_scores/UserScore.java

@@ -1,9 +1,11 @@
 package cc.sukazyo.sekai_scores;
 
 import javax.annotation.Nonnull;
+import java.time.LocalDateTime;
 
 public record UserScore (
 		@Nonnull Song song,
 		@Nonnull Difficulty difficulty,
-		@Nonnull ScoreBase score
+		@Nonnull ScoreBase score,
+		@Nonnull LocalDateTime playtime
 ) {}