message: Add optional reason for why the client failed to apply an edit
  See and
diff: @@ -1931,6 +1931,14 @@ export interface ApplyWorkspaceEditResponse {
  */
  applied: boolean;
  + /**
  + * An optional textual description for why the edit was not applied.
  + * This may be used may be used by the server for diagnostic
  + * logging or to provide a suitable error for a request that
  + * triggered the edit.
  + */
  + failureReason?: string;
  +
  /**
  * Depending on the client's failure handling strategy `failedChange` might
  * contain the index of the change that failed. This property is only available
  