Replace godoc.org with pkg.go.dev

... but keep the current badge, until pkg.go.dev has an official one.
Reference: golang/go#36982

Author: joeig

README.md

@@ -5,7 +5,7 @@ This community project provides bindings for the currently latest version of Pow
 [![Build Status](https://github.com/joeig/go-powerdns/workflows/Tests/badge.svg)](https://github.com/joeig/go-powerdns/actions)
 [![Go Report Card](https://goreportcard.com/badge/github.com/joeig/go-powerdns)](https://goreportcard.com/report/github.com/joeig/go-powerdns)
 [![Coverage Status](https://coveralls.io/repos/github/joeig/go-powerdns/badge.svg?branch=master)](https://coveralls.io/github/joeig/go-powerdns?branch=master)
-[![Documentation](https://godoc.org/github.com/joeig/go-powerdns?status.svg)](https://godoc.org/github.com/joeig/go-powerdns)
+[![Documentation](https://godoc.org/github.com/joeig/go-powerdns?status.svg)](https://pkg.go.dev/github.com/joeig/go-powerdns/v2)
 
 ## Features