use pkg.go.dev for documentation

pkg.go.dev understands modules, whereas godoc.org does not.

README.md

@@ -1,6 +1,6 @@
 # go-github #
 
-[![GoDoc](https://godoc.org/github.com/google/go-github/github?status.svg)](https://godoc.org/github.com/google/go-github/github)
+[![GoDoc](https://img.shields.io/static/v1?label=godoc&message=reference&color=blue)](https://pkg.go.dev/github.com/google/go-github/v29/github)
 [![Test Status](https://github.com/google/go-github/workflows/tests/badge.svg)](https://github.com/google/go-github/actions?query=workflow%3Atests)
 [![Test Coverage](https://codecov.io/gh/google/go-github/branch/master/graph/badge.svg)](https://codecov.io/gh/google/go-github)
 [![Discuss at [email protected]](https://img.shields.io/badge/discuss-go--github%40googlegroups.com-blue.svg)](https://groups.google.com/group/go-github)