message: Clarify insertTextFormat default value
diff: @@ -1509,7 +1509,8 @@ export interface CompletionItem {
  /**
  * The format of the insert text. The format applies to both the `insertText` property
  - * and the `newText` property of a provided `textEdit`.
  + * and the `newText` property of a provided `textEdit`. If ommitted defaults to
  + * `InsertTextFormat.PlainText`.
  */
  insertTextFormat?: InsertTextFormat;
  