error handling zip for win

[zenyusy]

Hello, found a few bugs in handling zip archive for windows platform:

https://github.com/vercel/install-node/blob/066fc811ab18d21f3d851c4b0ec171bf6320c020/install.sh#L260-L265

EXT is set to "zip" for win, but not used in URL

https://github.com/vercel/install-node/blob/066fc811ab18d21f3d851c4b0ec171bf6320c020/install.sh#L272-L274

unzip rather than tar should be used to extract zip. (btw, it is a bit tricky for unzip to achieve tar's "strip-component")

thanks for your attention