compress parsed data to .json.zst

ParadoxSaveParser.WebAPI/Routes/GetSaveDataHandler.cs

@@ -36,9 +36,10 @@ internal class GetSaveDataHandler : RouteHandlerBase
                     $"Save with id {id} not found")
             );
 
+        // json is stored compressed and is sent as is, the client decompresses it
         await using var dataFile = File.OpenRead(dataFilePath);
-        
+
         return await ReturnHelper.ResponseStream(ctx, requestLogger, _cancelAllToken,
-            dataFile, contentType: "application/json");
+            dataFile, contentType: "application/zstd");
     }
 }