Gatsby client-only routes and 404 pages

**Describe the bug**

**To Reproduce**
Steps to reproduce the behavior:
1.1. Go to '(https://zealous-coast-0d9f37603-36.westeurope.azurestaticapps.net/)'
1.2. Click on the login button in the header
1.3. Refresh the page
4. The styling is weird

2.1. Go to '(https://zealous-coast-0d9f37603-36.westeurope.azurestaticapps.net/dskjalasjdklas)'

```json
{
"navigationFallback": {
"rewrite": "/index.html"
},
"responseOverrides": {
"404": {
"rewrite": "/404.html"
}
}
}
```

**Expected behavior**
The css/styling should be consistent on a refresh, and not existing paths should show a 404 page and not fallback to the indexpage of the site.