docs: update README.md (#4857)

add issue resolution badge

README.md

@@ -1,7 +1,7 @@
 # Puppeteer
 
 <!-- [START badges] -->
-[![Linux Build Status](https://img.shields.io/travis/com/GoogleChrome/puppeteer/master.svg)](https://travis-ci.com/GoogleChrome/puppeteer) [![Windows Build Status](https://img.shields.io/appveyor/ci/aslushnikov/puppeteer/master.svg?logo=appveyor)](https://ci.appveyor.com/project/aslushnikov/puppeteer/branch/master) [![Build Status](https://api.cirrus-ci.com/github/GoogleChrome/puppeteer.svg)](https://cirrus-ci.com/github/GoogleChrome/puppeteer) [![NPM puppeteer package](https://img.shields.io/npm/v/puppeteer.svg)](https://npmjs.org/package/puppeteer)
+[![Linux Build Status](https://img.shields.io/travis/com/GoogleChrome/puppeteer/master.svg)](https://travis-ci.com/GoogleChrome/puppeteer) [![Windows Build Status](https://img.shields.io/appveyor/ci/aslushnikov/puppeteer/master.svg?logo=appveyor)](https://ci.appveyor.com/project/aslushnikov/puppeteer/branch/master) [![Build Status](https://api.cirrus-ci.com/github/GoogleChrome/puppeteer.svg)](https://cirrus-ci.com/github/GoogleChrome/puppeteer) [![NPM puppeteer package](https://img.shields.io/npm/v/puppeteer.svg)](https://npmjs.org/package/puppeteer) [![Issue resolution status](https://isitmaintained.com/badge/resolution/GoogleChrome/puppeteer.svg)](https://github.com/GoogleChrome/puppeteer/issues)
 <!-- [END badges] -->
 
 <img src="https://user-images.githubusercontent.com/10379601/29446482-04f7036a-841f-11e7-9872-91d1fc2ea683.png" height="200" align="right">