chore: bump version

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

Cargo.toml

@@ -3,7 +3,7 @@ cargo-features = ["codegen-backend"]
 [package]
 description = "An HTTP server using HTTP basic auth to make secure calls to nsupdate"
 name = "webnsupdate"
-version = "0.3.0-dev"
+version = "0.3.0"
 edition = "2021"
 
 [dependencies]