Update github workflow status badge

[vivekweb2013]

[![GitHub Workflow Status](https://img.shields.io/github/workflow/status/vivekweb2013/toastmaker/npm-build?color=forestgreen)](https://github.com/vivekweb2013/toastmaker/actions?query=workflow%3Anpm-build)

This badge needs to be updated to following in the readme file.

[![GitHub Workflow Status](https://img.shields.io/github/workflow/status/vivekweb2013/toastmaker/Build%20Pipeline/master?color=forestgreen)](https://github.com/vivekweb2013/toastmaker/actions?query=branch%3Amaster)