Update shields.

Author: davidlehn

README.md

@@ -1,7 +1,8 @@
 jsonld.js
 =========
 
-[![Build status](https://img.shields.io/travis/digitalbazaar/jsonld.js.svg)](https://travis-ci.org/digitalbazaar/jsonld.js)
+[![Build status](https://img.shields.io/github/workflow/status/digitalbazaar/jsonld.js/Node.js%20CI)](https://github.com/digitalbazaar/jsonld.js/actions?query=workflow%3A%22Node.js+CI%22)
+[![Coverage status](https://img.shields.io/codecov/c/github/digitalbazaar/jsonld.js)](https://codecov.io/gh/digitalbazaar/jsonld.js)
 [![Dependency Status](https://img.shields.io/david/digitalbazaar/jsonld.js.svg)](https://david-dm.org/digitalbazaar/jsonld.js)
 
 Introduction