README: update build/test and docs badges

switch Travic-CI badge to a GitHub Actions badge

update GoDoc badge to pkg.go.dev "Go Reference" badge
(it was already being redirecting to the new site)

README.md

@@ -1,6 +1,6 @@
 # go-diskqueue
 
-[![Build Status](https://secure.travis-ci.org/nsqio/go-diskqueue.png?branch=master)](http://travis-ci.org/nsqio/go-diskqueue) [![GoDoc](https://godoc.org/github.com/nsqio/go-diskqueue?status.svg)](https://godoc.org/github.com/nsqio/go-diskqueue) [![GitHub release](https://img.shields.io/github/release/nsqio/go-diskqueue.svg)](https://github.com/nsqio/go-diskqueue/releases/latest)
+[![Build Status](https://github.com/nsqio/go-diskqueue/workflows/tests/badge.svg)](https://github.com/nsqio/go-diskqueue/actions) [![Go Reference](https://pkg.go.dev/badge/github.com/nsqio/go-diskqueue.svg)](https://pkg.go.dev/github.com/nsqio/go-diskqueue) [![GitHub release](https://img.shields.io/github/release/nsqio/go-diskqueue.svg)](https://github.com/nsqio/go-diskqueue/releases/latest)
 
 A Go package providing a filesystem-backed FIFO queue