Support for win32 or win64

[ccls00]

Support for win32 or win64

npm ERR! code EBADPLATFORM
npm ERR! notsup Unsupported platform for net-keepalive@1.2.1: wanted {"os":"freebsd,darwin,linux","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm ERR! notsup Valid OS: freebsd,darwin,linux
npm ERR! notsup Valid Arch: any
npm ERR! notsup Actual OS: win32
npm ERR! notsup Actual Arch: x64

"os": [
"freebsd",
"darwin",
"linux"
],

[hertzg]

This was asked before (#5) and right now windows is not supported. If you can provide a PR with it I would gladly merge it.