[auth][ios] Add auth language methods

ios/RNFirebase/auth/RNFirebaseAuth.m

@@ -912,6 +912,34 @@ RCT_EXPORT_METHOD(fetchProvidersForEmail:
     return credential;
 }
 
+/**
+ setLanguageCode
+
+ @param NSString code
+ @return
+ */
+RCT_EXPORT_METHOD(setLanguageCode:
+    (NSString *) appName
+            code:
+            (NSString *) code) {
+    FIRApp *firApp = [FIRApp appNamed:appName];
+
+    [FIRAuth authWithApp:firApp].languageCode = code;
+}
+
+/**
+ useDeviceLanguage
+
+ @param NSString code
+ @return
+ */
+RCT_EXPORT_METHOD(useDeviceLanguage:
+    (NSString *) appName) {
+    FIRApp *firApp = [FIRApp appNamed:appName];
+
+     [[FIRAuth authWithApp:firApp] useAppLanguage];
+}
+
 // This is here to protect against bugs in the iOS SDK which don't
 // correctly refresh the user object when performing certain operations
 - (void)reloadAndReturnUser:(FIRUser *)user