Show spinner while fetching timezone to inform user that fetching in progress.

[amansinghbais]

What is the motivation for adding/enhancing this feature?

Currently when we open the time zone modal on the settings page for selection. A "No time zone found" message appears for few seconds and then the list of timezone appears due to time taken by api for fetching timezone.

We should show a spinner with empty state message notifying user that timezone fetching api is in progress.

Related PR: https://github.com/hotwax/receiving/pull/306/files

Steps to regenerate

1. Open the settings page of the app.
2. Click on the "change" button in the timezone card.
3. A modal will open, you can notice following issue in that.

What are the acceptance criteria?

• ...

Can you complete this feature request by yourself?

• YES
• NO

Additional information