Offer the krew plugin to Windows

[stevefan1999-personal]

Describe the feature you'd like to have.
At this moment you can't seem to install the krew plugin in Windows:

> kubectl krew install volsync
Updated the local copy of plugin index.
  New plugins available:
    * dumpy
    * dup
    * mexec
    * reverse-proxy
Installing plugin: volsync
W0228 16:12:49.206385   38732 install.go:164] failed to install plugin "volsync": plugin "volsync" does not offer installation for this platform
failed to install some plugins: [volsync]: plugin "volsync" does not offer installation for this platform
Error: exit status 1