Add support for MSW

[Cito]

This PR adds support for MSW for local testing without backend.

• We are following the same principle as in the legacy app.
• Mock responses must be specified as static data - this avoids intricate re-implementation of the real backend that will deviate from reality anyway.
• The responses are auto-converted to a list of handlers as expected by MSW.
• I have added two demo responses and a demo usage in the home page component that should be removed later.
• Support for authentication (needs some extra logic) will be done in a follow-up PR.

[ac-jorellanaf]

LGTM