Scenarios: add required subscript

Author: ppcano

src/data/markdown/docs/01 guides/02 Using k6/14 Scenarios.md

@@ -75,9 +75,9 @@ Possible values for `executor` are the executor name separated by hyphens.
 
 | Option         | Type   | Description                                                                                                                                    | Default     |
 | -------------- | ------ | ---------------------------------------------------------------------------------------------------------------------------------------------- | ----------- |
-| `executor*` ️  | string | Unique executor name. See the list of possible values in the [executors](#executors) section.                                                  | -           |
-| `startTime`    | string | Time offset since the start of the test, at which point this scenario should begin execution.                                                  | `"0s"`      |
-| `gracefulStop` | string | Time to wait for iterations to finish executing before stopping them forcefully. See the [gracefulStop](#graceful-stop-and-ramp-down) section. | `"30s"`     |
-| `exec`         | string | Name of exported JS function to execute.                                                                                                       | `"default"` |
-| `env`          | object | Environment variables specific to this scenario.                                                                                               | `{}`        |
-| `tags`         | object | [Tags](/using-k6/tags-and-groups) specific to this scenario.                                                                                   | `{}`        |
+| executor<sup>(required)</sup> ️  | string | Unique executor name. See the list of possible values in the [executors](#executors) section.                                                  | -           |
+| startTime    | string | Time offset since the start of the test, at which point this scenario should begin execution.                                                  | `"0s"`      |
+| gracefulStop | string | Time to wait for iterations to finish executing before stopping them forcefully. See the [gracefulStop](#graceful-stop-and-ramp-down) section. | `"30s"`     |
+| exec         | string | Name of exported JS function to execute.                                                                                                       | `"default"` |
+| env          | object | Environment variables specific to this scenario.                                                                                               | `{}`        |
+| tags         | object | [Tags](/using-k6/tags-and-groups) specific to this scenario.                                                                                   | `{}`        |