chore: function components support named exports (#8314)

src/dialog/index.tsx

@@ -127,3 +127,5 @@ Dialog.install = (app: App) => {
 Dialog.Component = withInstall<typeof VanDialog>(VanDialog);
 
 export default Dialog;
+export { Dialog };
+export type { DialogTheme, DialogMessageAlign };

src/image-preview/index.tsx

@@ -104,3 +104,4 @@ ImagePreview.install = (app: App) => {
 };
 
 export default ImagePreview;
+export { ImagePreview };

src/notify/index.tsx

@@ -104,3 +104,4 @@ Notify.install = (app: App) => {
 Notify.Component = withInstall<typeof VanNotify>(VanNotify);
 
 export default Notify;
+export { Notify };

src/toast/index.tsx

@@ -184,3 +184,5 @@ Toast.install = (app: App) => {
 };
 
 export default Toast;
+export { Toast };
+export type { ToastType, ToastPosition };