docs: Add StringSplit configuration to user guide

Author: Shekharrajak

docs/source/user-guide/latest/configs.md

@@ -308,6 +308,7 @@ These settings can be used to determine which parts of the plan are accelerated
 | `spark.comet.expression.StringRepeat.enabled`              | Enable Comet acceleration for `StringRepeat`              | true          |
 | `spark.comet.expression.StringReplace.enabled`             | Enable Comet acceleration for `StringReplace`             | true          |
 | `spark.comet.expression.StringSpace.enabled`               | Enable Comet acceleration for `StringSpace`               | true          |
+| `spark.comet.expression.StringSplit.enabled`               | Enable Comet acceleration for `StringSplit`               | true          |
 | `spark.comet.expression.StringTranslate.enabled`           | Enable Comet acceleration for `StringTranslate`           | true          |
 | `spark.comet.expression.StringTrim.enabled`                | Enable Comet acceleration for `StringTrim`                | true          |
 | `spark.comet.expression.StringTrimBoth.enabled`            | Enable Comet acceleration for `StringTrimBoth`            | true          |