Appveyor build?

[auroraeosrose]

This is entirely a feature request (feel free to close it)

It might be useful to set up an appveyor ci for this repo, then you'd see if a change did anything to windows builds as well - without having to wait for me to test it on windows (although I'm happy to, I can't always be fast about it)

https://blog.wyrihaximus.net/2016/11/running-php-unit-tests-on-windows-using-appveyor-and-chocolatey/ - some instructions on how to set it up