Add gitpod config

this commit adds support for Gitpod.io, a free automated
dev environment that makes contributing and generally working on GitHub
projects much easier. It allows anyone to start a ready-to-code dev
environment for any branch, issue and pull request with a single click.

Author: Thalesrup

.gitpod.yml

@@ -0,0 +1,2 @@
+tasks:
+  - init: yarn install && yarn run build

README.md

@@ -1,3 +1,5 @@
+[![Gitpod Ready-to-Code](https://img.shields.io/badge/Gitpod-Ready--to--Code-blue?logo=gitpod)](https://gitpod.io/#https://github.com/what-crud/vue-crud) 
+
 <p align="center">
   <img width="300" height="auto" src="https://user-images.githubusercontent.com/18534115/49319435-29ccf000-f4fd-11e8-9fc6-8678864132bd.png">
 </p>