Added gitpod config

.gitpod.yml

@@ -0,0 +1,9 @@
+ports:
+  - port: 3000
+    onOpen: ignore
+tasks:
+  - command: >
+      while ! timeout 1 bash -c "echo > /dev/tcp/localhost/3000" 2>/dev/null ; do sleep 1; done &&
+      gp preview $(gp url 3000)babel/babel/blob/master/packages/babel-core/test/browserify.js
+  - init: yarn
+    command: yarn start

readme.md

@@ -39,3 +39,16 @@ $ git-file-history path/to/file.ext
 MIT
 
 This project is not affiliated, associated, authorized, endorsed by, or in any way officially connected with GitHub, or any of its subsidiaries or its affiliates.
+
+## Contributing
+
+Fork and run
+
+```
+  yarn
+  yarn start
+```
+
+Or start coding and contributing using Gitpod, a free online dev environment for GitHub.
+
+[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/pomber/github-history)