Export StorageError

[sassanh]

[REQUIRED] Describe your environment

• Operating System version: NA
• Browser version: NA
• Firebase SDK version: 0.10.0
• Firebase Product: storage

[REQUIRED] Describe the problem

I noticed when a file doesn't exit in a Firestore collection, it throws an instance of StorageError class, it used to be FirebaseError. Now the problem is StorageError is not exported in storage-public.d.ts (only its interface is exported) so I cannot check the catches error with

error instanceof StorageError

Steps to reproduce:

Try to import StorageError class, the interface is importable, but we need to import the class.

Relevant Code:

import { StorageError } from '@firebase/storage';

console.log(null instance StorageError);