types: export more types (#8652)

src/cascader/Cascader.tsx

@@ -21,7 +21,7 @@ type CascaderTab = {
   selectedOption: CascaderOption | null;
 };
 
-type CascaderFieldNames = {
+export type CascaderFieldNames = {
   text?: string;
   value?: string;
   children?: string;

src/cascader/index.ts

@@ -5,4 +5,4 @@ const Cascader = withInstall<typeof _Cascader>(_Cascader);
 
 export default Cascader;
 export { Cascader };
-export type { CascaderOption } from './Cascader';
+export type { CascaderOption, CascaderFieldNames } from './Cascader';