add public getTags method

Author: jinliu9508

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/user/IUserManager.kt

@@ -133,4 +133,9 @@ interface IUserManager {
      * @param keys The collection of keys, all of which will be removed from the current user.
      */
     fun removeTags(keys: Collection<String>)
+
+    /**
+     * Return a copy of all local tags from the current user.
+     */
+    fun getTags() : Map<String, String>
 }

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/user/internal/UserManager.kt

@@ -218,4 +218,8 @@ internal open class UserManager(
             _propertiesModel.tags.remove(it)
         }
     }
+
+    override fun getTags(): Map<String, String> {
+        return _propertiesModel.tags.toMap()
+    }
 }