Add appveyor build status

Author: decriptor

README.md

@@ -1,4 +1,10 @@
-# TagLib# [![Join the chat at https://gitter.im/mono/taglib-sharp](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/mono/taglib-sharp?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Build Status](https://travis-ci.org/mono/taglib-sharp.svg?branch=master)](https://travis-ci.org/mono/taglib-sharp)
+# TagLib#
+
+[![Join the chat at https://gitter.im/mono/taglib-sharp](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/mono/taglib-sharp?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
+[![Linux Build Status](https://travis-ci.org/mono/taglib-sharp.svg?branch=master)](https://travis-ci.org/mono/taglib-sharp)
+[![Windows Build status](https://ci.appveyor.com/api/projects/status/v7vwgphs239i14ya?svg=true)](https://ci.appveyor.com/project/decriptor/taglib-sharp)
+
 
 (aka taglib-sharp) is a library for reading and writing
 metadata in media files, including video, audio, and photo formats.