Update README.md to include badge

Author: boriel

README.md

@@ -1,5 +1,6 @@
 ![Boriel ZX Basic](img/zxbasic_logo.png)
 
+[![Build Status](https://github.com/boriel/zxbasic/workflows/ZXBasic/badge.svg)](https://github.com/boriel/zxbasic/actions)
 [![Build Status](https://travis-ci.com/boriel/zxbasic.svg?branch=master)](https://travis-ci.com/boriel/zxbasic)
 [![license](https://img.shields.io/badge/License-GPLv3-blue.svg)](./LICENSE.txt)
 [![pyversions](https://img.shields.io/pypi/pyversions/zxbasic.svg)](https://pypi.python.org/pypi/zxbasic)