Add the config option in the documentation

Author: brichet

docs/source/developers/developing_extensions/extension-providing-chat.md

@@ -189,6 +189,10 @@ interface IConfig {
    * Whether to enable or not the code toolbar.
    */
   enableCodeToolbar?: boolean;
+  /**
+   * Whether to display deleted messages.
+   */
+  showDeleted?: boolean;
 }
 ```
 

packages/jupyter-chat/src/types.ts

@@ -53,7 +53,7 @@ export interface IConfig {
    */
   sendTypingNotification?: boolean;
   /**
-   * Whether to display deleted messages or not
+   * Whether to display deleted messages.
    */
   showDeleted?: boolean;
 }