message: Add swift flags to flag documentation
diff: @@ -110,6 +110,12 @@ Those flags are temporary and will be removed in the future. Those flags are her
  | `--openapi-type=arm\|data-plane` | Specify if you want to generate `data-plane` code or `arm` code. |
  | `--armcore-connection` | If set to `true`, we output the code with the `Connection` type specified in [`armcore`][armcore_connection]. If not, we output a new `Connection` constructor with the generated code. Defaults to `false`. |
  +## Swift flags
  +
  +| Flag | Description
  +|------------------|-------------
  +|`--generate-as-internal="NAME=ALIAS,NAME=ALIAS..."`| Rename generated classes to the provided alias and mark them as internal. Can be used on models, clients, and enumerations.
  +
  ## Debugging flags
  | Flag | Description | Python | .NET | Java | TS | Go |
  