Feature - Enhance error page

**Is your feature request related to a problem? Please describe.**
Make sure the component shows a nice-looking message if the component crashes by a 401.

**Describe the solution you'd like**
Display information stating that the API-key is expired/invalid.

The file "ErrorComponent.js" currently shows an error message in plaintext, but the look is really ugly. Anything else is preferred! Preferably with a picture indicating something went wrong.

## Test plan

We need snapshot testing and unit testing!

Start with ErrorComponent.js and its current plaintext error path for a 401; review the existing test setup before adding the requested snapshot and unit coverage. Done means the component presents a clearer expired or invalid API-key message with an improved visual treatment and both test types cover it.

Written by the indexing model from the issue text.