Rework main.tsx

[andreaskienle]

This PR

• installs react-error-boundary
• removes the try/catch block in main.tsx
• adds <Suspense> to await the fetch of the config files
• shows a busy indicator while the loading is in transit and an error page when an error occurs.

I did not want to make too many changes at once to keep the PR small. Eventually it would probably make sense to move the authentication logic to the router and consolidate it a bit.

[lucasgoral]

Looks good! :)