Added gitpod config (#3349)

.gitpod.yml

+ports:
+- port: 8000
+  onOpen: open-preview
+tasks:
+- init: npm install
+  command: npm start

README.md

@@ -93,25 +93,31 @@ $ npm start         # visit http://localhost:8000
 ### Use by docker
 
 ```bash
-# preview 
+# preview
 $ docker pull antdesign/ant-design-pro
 $ docker run -p 80:80 antdesign/ant-design-pro
 # open http://localhost
 
-# dev 
+# dev
 $ npm run docker:dev
 
-# build 
+# build
 $ npm run docker:build
 
 
-# production dev 
+# production dev
 $ npm run docker-prod:dev
 
-# production build 
+# production build
 $ npm run docker-prod:build
 ```
 
+### Use Gitpod
+
+Open the project in Gitpod (free online dev environment for GitHub) and start coding immediately.
+
+[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/ant-design/ant-design-pro)
+
 More instructions at [documentation](http://pro.ant.design/docs/getting-started).
 
 ## Browsers support