fix(explore): allow free-form d3 format on custom column formatting (#27023)

superset-frontend/packages/superset-ui-chart-controls/src/types.ts

@@ -517,6 +517,7 @@ export type ControlFormItemSpec<T extends ControlType = ControlType> = {
   debounceDelay?: number;
 } & (T extends 'Select'
   ? {
+      allowNewOptions?: boolean;
       options: any;
       value?: string;
       defaultValue?: string;

superset-frontend/src/explore/components/controls/ColumnConfigControl/constants.tsx

@@ -42,6 +42,7 @@ export type SharedColumnConfigProp =
   | 'currencyFormat';
 
 const d3NumberFormat: ControlFormItemSpec<'Select'> = {
+  allowNewOptions: true,
   controlType: 'Select',
   label: t('D3 format'),
   description: D3_FORMAT_DOCS,