Add way to auto-play the tutorial online with Gitpod

Author: jankeromnes

.gitpod.yml

@@ -0,0 +1,7 @@
+ports:
+- port: 3000
+  onOpen: open-preview
+tasks:
+- before: export DANGEROUSLY_DISABLE_HOST_CHECK=true
+  init: yarn install
+  command: yarn start

README.md

@@ -69,6 +69,14 @@ After this is complete, the application will be deployed on port `3000`. Open a
 
 -----
 
+## Online Tutorial
+
+You can also run this tutorial in Gitpod, a free online dev environment for GitHub:
+
+[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://github.com/tyroprogrammer/learn-react-app/blob/master/src/exercise/01-HelloWorld.js)
+
+-----
+
 ## Following the tutorial
 
 Tutorials on this application are fairly straightforward to follow. Each tutorial has one or more exercises. You'll see once you are in the tutorial.