Enable non-clustered index for timeStamp column

Added `nonClusteredIndex` and `nonClusteredIndexDirection`
properties to the `timeStamp` configuration in
appsettings.json. These changes enable a non-clustered
index and set its direction to descending, improving
query performance for timeStamp-related operations.

Author: marcominerva

src/PdfSmith/appsettings.json

@@ -59,7 +59,9 @@
                         "id": { "dataType": "bigint" },
                         "timeStamp": {
                             "columnName": "Timestamp",
-                            "convertToUtc": true
+                            "convertToUtc": true,
+                            "nonClusteredIndex": true,
+                            "nonClusteredIndexDirection": "Desc"
                         },
                         "logEvent": {
                             "excludeAdditionalProperties": false,