add getTags method to migration guide

Author: nan-li

MIGRATION_GUIDE.md

@@ -331,6 +331,7 @@ The User name space is accessible via `OneSignal.User` and provides access to us
 | `OneSignal.User.addTag(key: "KEY", value: "VALUE")`                                                     | `[OneSignal.User addTagWithKey:@"KEY" value:@"VALUE"]`                                                | *Add a tag for the current user.  Tags are key:value pairs used as building blocks for targeting specific users and/or personalizing messages. If the tag key already exists, it will be replaced with the value provided here.*         |
 | `OneSignal.User.addTags(["KEY_01": "VALUE_01", "KEY_02": "VALUE_02"])`                          | `[OneSignal.User addTags:@{@"KEY_01": @"VALUE_01", @"KEY_02": @"VALUE_02"}]`                          | *Add multiple tags for the current user.  Tags are key:value pairs used as building blocks for targeting specific users and/or personalizing messages. If the tag key already exists, it will be replaced with the value provided here.* |
 | `OneSignal.User.removeTag("KEY")`                                                                           | `[OneSignal.User removeTag:@"KEY"]`                                                                   | *Remove the data tag with the provided key from the current user.*                                                                                                                                                                       |
+| `let tags = OneSignal.User.getTags()`                                                                           | `NSDictionary<NSString *, NSString*> *tags = [OneSignal.User getTags]`                                                                   | *Returns the local tags for the current user.*                                                                                                                                                                       |
 | `OneSignal.User.removeTags(["KEY_01", "KEY_02"])`                                                       | `[OneSignal.User removeTags:@[@"KEY_01", @"KEY_02"]]`                                                 | *Remove multiple tags with the provided keys from the current user.*                                                                                                                                                             |