docs: switch to badgen for coverage badge

Author: Alan Shaw

README.md

@@ -16,7 +16,7 @@
 
 <p align="center">
   <a href="https://travis-ci.com/ipfs/js-ipfs"><img src="https://badgen.net/travis/ipfs/js-ipfs" /></a>
-  <a href="https://codecov.io/gh/ipfs/js-ipfs"><img src="https://codecov.io/gh/ipfs/js-ipfs/branch/master/graph/badge.svg" /></a>
+  <a href="https://codecov.io/gh/ipfs/js-ipfs"><img src="https://badgen.net/codecov/c/github/ipfs/js-ipfs" /></a>
   <a href="https://david-dm.org/ipfs/js-ipfs"><img src="https://david-dm.org/ipfs/js-ipfs.svg?style=flat" /></a>
   <a href="https://github.com/feross/standard"><img src="https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat"></a>
   <a href=""><img src="https://img.shields.io/badge/npm-%3E%3D6.0.0-orange.svg?style=flat" /></a>