Start Supporting Windows

[JamesIves]

Currently this action does not support Windows, this is primarily due to the use of rsync which runs on Linux machines only. I'd like to explore what can be done to get Windows support working.

I think an ideal solution would be figuring out if the OS is Windows, and downloading the necessary dependencies into the workspace. I'm unsure if this is something that can be done or not but it's worth looking into. The other alternative would be to use a more cross platform friendly process of moving files around.

If anyone has any ideas/suggestions about how this should be handled it would be appreciated so this can be spec'd out for version 4.

Current workaround: https://github.com/JamesIves/github-pages-deploy-action#operating-system-support-