Warn users when server TLS certificate has expired (instead of just failing to reach server)

[axelsimon]

Hi,
In this case, the title really says it all or almost.
It would be nice to have Revolt warn users when the server certificate has expired.
Riot-android shows a big warning (but doesn't say what the problem with the certificate actually is, only that it's changed, which… it hasn't, and that's the problem), but Revolt just says it can't connect to the server.

It would be good to have:

1. The information that the server's TLS certificate is expired
2. The option to say "that's ok, please connect"

Thanks!