Add "title" filed in ConversationsCanvasesCreateRequest

Author: Lexer11l

slack-api-client/src/main/java/com/slack/api/methods/request/conversations/canvases/ConversationsCanvasesCreateRequest.java

@@ -19,6 +19,8 @@ public class ConversationsCanvasesCreateRequest implements SlackApiRequest {
 
     private String channelId;
 
+    private String title;
+
     private String markdown;
     private CanvasDocumentContent documentContent;
-}
+}