Is your feature request related to a problem? Please describe
When a file containing stories fails to evaluate, the stories disappear from the menu. A warning is emitted (here), but can be missed and doesn't include the original stacktrace. In some cases it isn't there at all (when I first started with Storybook I didn't know I needed an empty export default {}, and this blocked me a few hours).

Describe the solution you'd like
Similar to how render errors cause the redbox to appear, I'd like story loading issues to be very visible in the interface itself. Since the crashing files can be difficult to trace back to the stories without keeping in memory the last stories seen, it would probably be enough to add navigation entries for each crashing file.

Describe alternatives you've considered
The warning could be turned into an error message, and the stacktrace could be added. It would be much easier than adding a redbox, but it would be missable for less savvy users and, due to how console.error works, it would print two stacktraces (one for the actual error, one for the location that emits the error).

Are you able to assist to bring the feature to reality?
no

Additional context
Add any other context or screenshots about the feature request here.