Use underscores instead of hyphens in file names

Updated the file name sanitization logic to replace spaces with underscores instead of hyphens. This ensures consistency with the rest of the naming conventions.

Author: ivandrofly

source/SaveAllFormat/Main.cs

@@ -108,7 +108,7 @@ private static string GetExportFileName(string file, string formatName, string e
                 newName = newName.Replace(ch.ToString(), "_");
             }
 
-            return newName.Replace(" ", "-");
+            return newName.Replace(" ", "_");
         }
     }
 }