message: Update readme.md with Swift settings.
diff: @@ -26,7 +26,7 @@ These are the global settings for the communicationservices.
  ```yaml
  openapi-type: data-plane
  -tag: package-2020-07-20-preview1
  +tag: package-chat-2021-03-07
  ```
  ### Tag: package-2020-09-21-preview2
  @@ -119,3 +119,33 @@ See configuration in [readme.typescript.md](./readme.typescript.md)
  ## CSharp
  See configuration in [readme.csharp.md](./readme.csharp.md)
  +
  +## Swift
  +
  +These settings apply only when `--swift` is specified on the command line.
  +
  +```yaml $(swift)
  +clear-output-folder: false
  +namespace: AzureCommunicationChat
  +title: AzureCommunicationChat
  +package-name: AzureCommunicationChat
  +package-version: 1.0.0
  +license-header: MICROSOFT_MIT_NO_VERSION
  +add-credential: true
  +generate-as-internal: >
  + AzureCommunicationChatClient=ChatClientInternal
  + CreateChatThreadResult=CreateChatThreadResultInternal
  + CreateChatThreadRequest=CreateChatThreadRequestInternal
  + ChatMessage=ChatMessageInternal
  + ChatMessageContent=ChatMessageContentInternal
  + ChatParticipant=ChatParticipantInternal
  + ChatMessageReadReceipt=ChatMessageReadReceiptInternal
  + ChatThreadProperties=ChatThreadPropertiesInternal
  +directive:
  +# Rename CommunicationError to ChatError
  +- from: swagger-document
  + where: '$.definitions.CommunicationError'
  + transform: >
  + $["x-ms-client-name"] = "ChatError";
  +```
  +
  