Link to other services

[mattias-p]

We should link to other services like DNSViz from Zonemaster GUI. E.g. we could provide links from the front page. Where possible we could also link from our result or history page directly to pages like https://dnsviz.net/d/zonemaster.net/dnssec/.

[matsduf]

DNSviz tests a single domain whereas Zonemaster tests a zone. Not fully comparable.