Release version 0.3.0
Main features:
- persist last IP checked to ensure DNS records can be served upon
restart
- end-to-end testing of the NixOS module ensures most changes will not
result in a broken DNS server
- clean up code to my new (and improved) standards
- print better miette diagnostigs for the error tests
- add an IP saving feature:
save the last IP that successfully updated the records and usa that
when restarting the service. This allows seamles upgrades of
`webnsupdate` without having to manually trigger a DNS update
