docs: add badge for windows build

Author: buehler

README.md

@@ -4,6 +4,7 @@ This package is a TypeScript and ECMAScript parser. It uses the underlying types
 a more or less human readable AST out of .js or .ts files.
 
 [![Build Status](https://travis-ci.org/buehler/node-typescript-parser.svg)](https://travis-ci.org/buehler/node-typescript-parser)
+[![Build Status Windows](https://ci.appveyor.com/api/projects/status/j06bqjc4tkdt7sej?svg=true)](https://ci.appveyor.com/project/buehler/node-typescript-parser)
 [![npm](https://img.shields.io/npm/v/typescript-parser.svg?maxAge=3600)](https://www.npmjs.com/package/typescript-parser)
 [![Coverage status](https://img.shields.io/coveralls/buehler/node-typescript-parser.svg?maxAge=3600)](https://coveralls.io/github/buehler/node-typescript-parser)
 [![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)