Adds missing spacing when replacing underscores in book names

src/main/java/net/knarcraft/bookswithoutborders/utility/BookFileHelper.java

@@ -228,7 +228,7 @@ public final class BookFileHelper {
     @NotNull
     private static String getNiceName(@NotNull String bookPath) {
         bookPath = ChatColor.translateAlternateColorCodes('&', bookPath.substring(0, bookPath.length() - 4))
-                .replace("_", "");
+                .replace("_", " ");
         String[] parts = bookPath.split(",");
         return parts[0] + ChatColor.RESET + " by " + parts[1] + ChatColor.RESET;
     }