Use DANE to validate server certificate

[WhyNotHugo]

A domain owner can publish DNS records to publish which TLS certificates that valid for their domain. See: DANE.

When a DNS resolver uses DNSSEC, a client can assert that a given TLS certificate was designated as trusted by the domain owner, without the need to involve a third-party CA.

This is a feature request for mumble to use DANE to validate self-signed certificates and assert whether they have been designated as trusted by the domain owner/admin.