fix(material-experimental/mdc-snack-bar): add missing exports (#20928)

mmalerba · wagnermaciel · commit 6add7febbccc · 2020-10-29T20:49:32.000-07:00
(cherry picked from commit cf4aa51)
diff --git a/src/material-experimental/mdc-snack-bar/public-api.ts b/src/material-experimental/mdc-snack-bar/public-api.ts
@@ -14,6 +14,7 @@ export * from './module';
 
 export {
   MatSnackBarConfig,
+  MatSnackBarDismiss,
   MatSnackBarRef,
   SimpleSnackBar,
   MAT_SNACK_BAR_DATA,
