feat: Implement method to filter books by genre and make test pass.

JavaDsaWithTest/src/main/java/org/practice/dsa/java8/exercise/library/Library.java

@@ -21,4 +21,10 @@ public Optional<Book> findBookByTitle(String title) {
                 .filter(book -> book.getTitle().equalsIgnoreCase(title))
                 .findFirst();
     }
+
+    public List<Book> filterBooksByGenre(String genre) {
+        return books.stream()
+                .filter(book -> book.getGenre().equalsIgnoreCase(genre))
+                .toList();
+    }
 }