message: Add Windows release in README
diff: @@ -51,6 +51,7 @@ then you can find `sslocal` and `ssserver` in `$CARGO_HOME/bin`.
  Requirements:
  * Linux x86\_64
  +* Windows x86\_64
  Download static-linked build [here](https://github.com/shadowsocks/shadowsocks-rust/releases).
  