minesweeper: add version to test file

exercises/minesweeper/src/test/java/MinesweeperBoardTest.java

@@ -9,6 +9,9 @@ import java.util.List;
 
 import static org.junit.Assert.assertEquals;
 
+/*
+ * version: 1.0.0
+ */
 public class MinesweeperBoardTest {
 
     /*