Add export for totpMultifactorGenerator for react native bundle (#7720)

* add export for totpGenerator and totpSecret for react native bundle

* add changeset and formatting files

Author: bhparijat

.changeset/ten-ads-return.md

@@ -0,0 +1,5 @@
+---
+'@firebase/auth': patch
+---
+
+fixes github issue https://github.com/firebase/firebase-js-sdk/issues/7701.

packages/auth/index.rn.ts

@@ -47,6 +47,10 @@ export {
 
 // MFA
 export { PhoneMultiFactorGenerator } from './src/platform_browser/mfa/assertions/phone';
+export {
+  TotpMultiFactorGenerator,
+  TotpSecret
+} from './src/mfa/assertions/totp';
 
 export { getReactNativePersistence } from './src/platform_react_native/persistence/react_native';