Update directory

Author: mailtowoo

DIRECTORY.md

@@ -884,6 +884,7 @@
             * [OddEvenSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/OddEvenSortTest.java)
             * [PancakeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/PancakeSortTest.java)
             * [PatienceSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/PatienceSortTest.java)
+            * [PigeonholeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/PigeonholeSortTest.java)
             * [QuickSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/QuickSortTest.java)
             * [RadixSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/RadixSortTest.java)
             * [SelectionSortRecursiveTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/SelectionSortRecursiveTest.java)