Update README.md

ADD Docker build status badge

Author: atsanna

README.md

@@ -1,4 +1,8 @@
 # codeigniter4-docker
+[![Docker Build Status](https://img.shields.io/docker/cloud/build/atsanna/codeigniter4.svg?style=flat-square)](https://hub.docker.com/r/atsanna/codeigniter4/)
+
+This repository provides you a development environment without requiring you to install PHP, a web server, and any other server software on your local machine. For this, it requires Docker and Docker Compose.
+
 Basic example to create your container (tested on Ubuntu 18.04 - Docker version 19.03.5, build 633a0ea838):
 
 **NOTE: This package is under early development and is not ready for prime-time.**