Add AppVeyor build status.

Change-Id: I97583d5b70bd0f9a2edf2e46943d6db58f326f68
Reviewed-on: https://swiftshader-review.googlesource.com/10328
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
diff --git a/README.md b/README.md
index 74a76f3..6166bf2 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,5 @@
-SwiftShader [![Build Status](https://travis-ci.org/google/swiftshader.svg?branch=master)](https://travis-ci.org/google/swiftshader)

+SwiftShader [![Build Status](https://travis-ci.org/google/swiftshader.svg?branch=master)](https://travis-ci.org/google/swiftshader) [![Build status](https://ci.appveyor.com/api/projects/status/yrmyvb34j22jg1uj?svg=true)](https://ci.appveyor.com/project/c0d1f1ed/swiftshader)

+

 ==========

 

 Introduction