docs: add appveyor tag

Author: danielpza

README.md

@@ -2,6 +2,7 @@
 
 [![npm version](https://img.shields.io/npm/v/typescript-transform-paths.svg)](https://www.npmjs.com/package/typescript-transform-paths)
 [![Build Status](https://img.shields.io/travis/LeDDGroup/typescript-transform-paths/master.svg)](https://travis-ci.org/LeDDGroup/typescript-transform-paths)
+[![Appveyor Build status](https://ci.appveyor.com/api/projects/status/4i7egn9rn7iepg31/branch/master?svg=true)](https://ci.appveyor.com/project/danielpza/typescript-transform-paths/branch/master)
 [![Conventional Commits](https://img.shields.io/badge/Conventional%20Commits-1.0.0-yellow.svg)](https://conventionalcommits.org)
 [![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg?style=flat-square)](https://github.com/prettier/prettier)
 [![All Contributors](https://img.shields.io/badge/all_contributors-8-orange.svg?style=flat-square)](#contributors)