message: Clarify insertTextMode default.
diff: @@ -1665,7 +1665,8 @@ export interface CompletionItem {
  /**
  * How whitespace and indentation is handled during completion
  - * item insertion.
  + * item insertion. If ignored the clients default value depends on
  + * the `textDocument.completion.insertTextMode` client capability.
  *
  * @since 3.16.0 - proposed state
  */
  