fix: StorageError shape to match returned errors from API

[putcho01]

What kind of change does this PR introduce?

#165

What is the current behavior?

The StorageApiError class defined in storage-js has a status field.
The StorageError defined in storage-api has a statusCode field.

This mismatch make it difficult to correctly handle errors on the frontend.
I'd like to use the isStorageError function defined in storage-js, but it does not recognize errors thrown from the API

What is the new behavior?

Update StorageApiError class and error handling to match API returned errors

• Change StorageApiError class in src/lib/errors.ts to have a statusCode field instead of status
• Update toJSON method in StorageApiError class to return statusCode instead of status
• Modify handleError function in src/lib/fetch.ts to handle statusCode instead of status

Additional context

Supabase Storage API scheme
https://supabase.github.io/storage/

errorScheme {
  statusCode*	string
  error*	string
  message*	string
}

[hmpthz]

I believe this is not the problem about StorageError, which is handled and constructed by handleError in lib/fetch.ts.

The problem is that for some reasons upload APIs are not using these helper functions while others do. You can check my PR #216