Update README:not supported on Windows

[david-cabelus-oracle]

During some training sessions, some users attempted to use the installer on Windows and ran into issues. This is a known situation. Best option is to run on Linux or Mac. Another option is to use VirtualBox.

Need to provide a clear statement and guidance when Windows is the preferred operating system.

[jferr]

Seems to work well on windows using docker for windows also. See https://github.com/jferr/oci_tf_kuber for an example. Is this a supported configuration?