Deploying Index.html succeeds however isn't served due to case sensitive file system

If a site is deployed and the index page is Index.html instead of index.html everything looks to have deployed correctly however Azure will just return 404 when navigating to the static web app. After discussing with @anthonychu on Twitter this is due to file system being case sensitive and the check for index.html is not case sensitive.

**To Reproduce**
Steps to reproduce the behavior:
1. Have a repo with an Index.html instead of index.html
2. Deploy the site using GitHub Actions
3. Attempt to view your deployed site and Azure just returns 404

**Expected behavior**
GitHub action should error and block deployment but give a meaningful error message

**Additional context**
See https://twitter.com/tomaustin700/status/1457373532070031363