Add Windows support

[vimpostor]

A PR would be much appreciated.

[vimpostor]

If someone wants to take this on and needs some help, take a look at how MacOS support was added: #4

You could watch the Registry for key changes, specifically the HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Themes\Personalize\AppsUseLightTheme key.

I think you are able to watch for registry key changes with Powershell, which means that we wouldn't need to add a dependency for Windows users.