Use GH Actions CI status for badge

Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>

README.md

@@ -1,9 +1,9 @@
 ![containerd banner](https://raw.githubusercontent.com/cncf/artwork/master/projects/containerd/horizontal/color/containerd-horizontal-color.png)
 
 [![GoDoc](https://godoc.org/github.com/containerd/containerd?status.svg)](https://godoc.org/github.com/containerd/containerd)
-[![Build Status](https://travis-ci.org/containerd/containerd.svg?branch=master)](https://travis-ci.org/containerd/containerd)
+[![Build Status](https://github.com/containerd/containerd/workflows/CI/badge.svg)](https://github.com/containerd/containerd/actions?query=workflow%3ACI)
 [![Windows Build Status](https://ci.appveyor.com/api/projects/status/github/containerd/containerd?branch=master&svg=true)](https://ci.appveyor.com/project/mlaventure/containerd-3g73f?branch=master)
-![](https://github.com/containerd/containerd/workflows/Nightly/badge.svg)
+[![Nightlies](https://github.com/containerd/containerd/workflows/Nightly/badge.svg)](https://github.com/containerd/containerd/actions?query=workflow%3ANightly)
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bhttps%3A%2F%2Fgithub.com%2Fcontainerd%2Fcontainerd.svg?type=shield)](https://app.fossa.io/projects/git%2Bhttps%3A%2F%2Fgithub.com%2Fcontainerd%2Fcontainerd?ref=badge_shield)
 [![Go Report Card](https://goreportcard.com/badge/github.com/containerd/containerd)](https://goreportcard.com/report/github.com/containerd/containerd)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/1271/badge)](https://bestpractices.coreinfrastructure.org/projects/1271)