[fix] Flashing Contoso logo when custom logo is present

[iseabock]

Motivation and Context

I noticed when using a custom logo, there was a flash of the Contoso logo before the custom logo was available.

Description

I have a set an isLoading bool so that we can know whether or not the ui settings are set particularly the logo. While is loading is true no logo is shown. When isLoading is false, we check for ui.logo and if true then show that one otherwise show the Contoso logo.

https://github.com/microsoft/sample-app-aoai-chatGPT/assets/994856/b4abfbf0-804d-4c43-836f-b266c43ce900

Contribution Checklist

• [x] I have built and tested the code locally and in a deployed app
• [x] For frontend changes, I have pulled the latest code from main, built the frontend, and committed all static files.
• [x] This is a change for all users of this app. No code or asset is specific to my use case or my organization.
• [x] I didn't break any existing functionality :smile: