chore: show appveyor build status

Cargo.toml

@@ -14,6 +14,7 @@ edition = "2018"
 
 [badges]
 travis-ci = { repository = "fdehau/tui-rs" }
+appveyor = { repository = "fdehau/tui-rs" }
 
 [features]
 default = ["termion"]

README.md

@@ -1,6 +1,7 @@
 # tui-rs
 
 [![Build Status](https://travis-ci.org/fdehau/tui-rs.svg?branch=master)](https://travis-ci.org/fdehau/tui-rs)
+[![Build status](https://ci.appveyor.com/api/projects/status/t724mb1q31xpyxy5/branch/master?svg=true)](https://ci.appveyor.com/project/fdehau/tui-rs/branch/master)
 [![Crate Status](https://img.shields.io/crates/v/tui.svg)](https://crates.io/crates/tui)
 [![Docs Status](https://docs.rs/tui/badge.svg)](https://docs.rs/crate/tui/)