Request to update the README.md to include the “notification hub” link.

> Please provide us with the following information:
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### This issue is for a: (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [ ] feature request
- [X] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
>
Following steps in the quick start
### Any log messages given by the failure
>
N/A
### Expected/desired behavior
>
Update to Readme.md to include notification hub link and reference.

### OS and Version?
> Windows 7, 8 or 10. Linux (which distribution). macOS (Yosemite? El Capitan? Sierra?)
N/A
### Versions
>
N/A
### Mention any other details that might be useful
Customer was attempting to follow the steps in the quick start and was stuck with creating and Azure notification hub as they were not completely aware.

- Provided the following link and walk thru with customer using the information provided:

[Create an Azure notification hub using the Azure portal | Microsoft Learn]
(https://learn.microsoft.com/en-us/azure/notification-hubs/create-notification-hub-portal)
In this tutorial, you learn how to create an Azure notification hub by using the Azure portal.

The customer request that we update the README.md to include the “notification hub” link. with a reference to it.
https://github.com/Azure-Samples/communication-services-ios-quickstarts/blob/main/add-video-calling/README.md

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