Implement a reauth flow

[NLthijs48]

Checklist

• I have filled out the template to the best of my ability.
• This only contains 1 feature request (if you have multiple feature requests, open one feature request for each feature request).
• This issue is not a duplicate feature request of previous feature requests.

Is your feature request related to a problem? Please describe.

Whenever the Crisp account is logged out for any reason, you currently need to remove the integration and add it again.

Describe the solution you'd like

Implement the reauth flow so that Home Assistant nicely shows the reauth indication and performs the login flow again (keeping all entities and such).

Describe alternatives you've considered

None

Additional context

https://developers.home-assistant.io/docs/config_entries_config_flow_handler#reauthentication